Suffering due to non-self-related preconceived notions in Theravada According to this answer:


  However, there is another type of suffering that cannot be fixed with
  anatta! This type of suffering comes from attachment to forms other
  than oneself, forms that have nothing to do with "I". For example,
  consider the situation when your teenage son suddenly declares that he
  is a gay person (a homosexual). Because you are so attached to an idea
  that your son should be a proper man, there is a great mismatch in
  your mind between expectation and reality. Because of this mismatch
  you experience dukkha, suffering. This type of dukkha has nothing to
  do with your sense of "I", it is about your son. But because you have
  a fixed idea of how things are supposed to be, you suffer whenever
  there is a mismatch.
  
  So (Theravada) anatta can't help with this type of suffering. 
  But (Mahayana) shunyata can.


Now this is a question directed to Theravada practitioners.

Let's say, somebody suffers from aversion when they see any person practising the gay lifestyle, because they have preconceived ideas about what is right or wrong about sexual orientation. This kind of suffering seems to be unrelated to craving or the self (because this is related to other unrelated people). Here, I use the example of a random stranger, not "my son".

Sexual orientation is just an example of a non-self-related preconceived notion. It could easily be something else like Brexit or communism or news of a natural disaster taking lives in a distant country.


According to Theravada and the Pali Canon, what is the cause of this suffering? Is it in any way related to the self, craving and dependent origination?
According to Theravada and the Pali Canon, how can this suffering be eliminated? According to the third noble truth, to end suffering, one must end craving. How does ending craving end this suffering?
Please provide references to the Pali Suttas, if possible.
I tried to do some research on this, from the Pali Canon, so I will post an answer.

A person may have a preconceived notion like the homosexual lifestyle is wrong, only the heterosexual lifestyle is correct. Or, communism and socialism are wrong, only democracy with capitalism is correct. Or, the view that the government must improve public transportation instead of building more roads is correct, while the view that the government must build more roads instead of improving public transportation instead is wrong.

The Mahayana view in general is that these preconceived notions or views are unrelated to the self and cannot be solved using anatta. Instead, the Mahayana shunyata must be used. If one can see that the sexual orientation, or political ideology, or government policies are truly without inherent substance, then one can avoid clinging to them, and thus be free of suffering.

While this sounds logical at a first glance, if we analyze this from a Theravada perspective, it is actually analyzing the wrong root cause. In my opinion, all types of suffering must have something to do with the self, however obscure this connection is. Why would I feel aversion at a concept or idea if it doesn't have anything to do with ME? There is obviously a clinging and I am clinging to it. I suffer not because a political ideology is real or unreal. I suffer because I cling to it. It has something to do with ME. The problem is that all of a person's views are relative to one's self or associated for or against one's self.

The following quotes from Sutta Nipata 4.5:


  When dwelling on views as "supreme," a person makes them the utmost
  thing in the world, &amp;, from that, calls all others inferior and so
  he's not free from disputes. When he sees his advantage in what's
  seen, heard, sensed, or in precepts &amp; practices, seizing it there he
  sees all else as inferior.


When one makes one view as correct, and all other views as incorrect, it's because he sees some advantage or something related to himself. There's a reason why he clings to it. For e.g. I may have other arguments why new roads should not be built, and instead public transportation must be improved. The real reason could be that I am afraid that if a new noisy highway is built next to my house, the property value of my house will drop. Hence, every argument that I have to support my view, has something to do with me.

For e.g. if I argue why Theravada is better than Mahayana, it may be because I associate myself with Theravada. If someone disparages Theravada, then I feel disparaged, because I assumed my self to be the mental fabrication.

So, this connection, may not be obvious. It may be obscure. But the connection of my view to my self definitely exists. And clinging of anything to the self, is related to one of the three types of craving.

Perhaps a person has strong views and scorn towards homosexuality, because he either feels it as challenging his own heterosexuality, or perhaps he is trying to hide his own closeted homosexuality. Or perhaps it conflicts with the teachings of the religion that he belongs to, or it conflicts with his father's teaching to him, which he clings to, because it comes from "my father". If it has nothing to do with him, then why would he be for or against it?

If news that trees in the Amazon rainforest got chopped down illegally in huge quantities reaches a person who stays in Russia, he might feel angry. Why? He may be a self-identified environmentalist who feels that nature and the environment belongs to him and his descendants, that his descendants are being deprived of their rightful inheritance. So, it has something to do with his self-interests.

A person disagrees with high taxation and good social welfare. Perhaps he works hard and makes a good income and does not want to share it with others. It's HIS income. Perhaps another person is poor and jobless, and would love to receive state help, so he publicly sides high taxation and good social welfare. It always has something to do with self-interests.

To be part of a religion or to be an environmentalist or to identify with a sexual orientation, sounds like craving of becoming. To enjoy sexual pleasures or state help in the form of food stamps, sounds like the craving of sensual pleasures. Craving leads to clinging. Clinging leads to becoming. These are part of dependent origination. Due to clinging, we may feel aversion when what we cling to is removed from us or is challenged.


  That, too, say the skilled, is a binding knot: that in dependence on
  which you regard another as inferior. So a monk shouldn't be dependent
  on what's seen, heard, or sensed, or on precepts &amp; practices; nor
  should he conjure a view in the world in connection with knowledge or
  precepts &amp; practices; shouldn't take himself to be "equal"; shouldn't
  think himself inferior or superlative.
  
  Abandoning what he had embraced, abandoning self, not clinging, he
  doesn't make himself dependent even in connection with knowledge;
  doesn't follow a faction among those who are split; doesn't fall back
  on any view whatsoever.


And so the Buddha tells that a monk should not become dependent on what is sensed, conjure a view in the world in connection with knowledge and compare himself or his interests against it.

The idea of comparing views and ideas against himself or his interests is continued in Sutta Nipata 4.9:


  Whoever construes 'equal,' 'superior,' or 'inferior,' by that he'd
  dispute; whereas to one unaffected by these three, 'equal,'
  'superior,' do not occur. Of what would the brahman say 'true' or
  'false,' disputing with whom: he in whom 'equal,' 'unequal' are not.


From Sutta Nipata 4.13:


  "Those who, dwelling on views, dispute, saying, 'Only this is true':
  do they all incur blame, or also earn praise there?"
  
  "[The praise:] It's such a little thing, not at all appeasing. I speak
  of two fruits of dispute; and seeing this, you shouldn't dispute —
  seeing the state where there's no dispute as secure. One who knows
  doesn't get involved in whatever are commonplace conventional views.
  One who is uninvolved: when he's forming no preference for what's
  seen, for what's heard, why would he get involved?


Here, we see that one dwelling on views, saying "only this is true", is actually because he developed a preference to it. Preference indicates that he formed an association with himself i.e. he assumed his self to be a mental fabrication, that is related to his view, or aligned with his self-interests.

From MN 22:


  "What do you think, monks: If a person were to gather or burn or do as
  he likes with the grass, twigs, branches &amp; leaves here in Jeta's
  Grove, would the thought occur to you, 'It's us that this person is
  gathering, burning, or doing with as he likes'?"
  
  "No, lord. Why is that? Because those things are not our self, nor do
  they belong to our self."
  
  "Even so, monks, whatever isn't yours: Let go of it. Your letting go
  of it will be for your long-term welfare &amp; happiness. And what isn't
  yours? Form isn't yours... Feeling isn't yours... Perception...
  Thought fabrications... Consciousness isn't yours: Let go of it. Your
  letting go of it will be for your long-term welfare &amp; happiness.


If a view has nothing to do with ME, why would I suffer from it? If a person burns leaves in a garden, why would I suffer from it, if I did not feel like those leaves belonged to me some how?

So, we only suffer from thought fabrications, preconceived views and opinions, because we think they are our's, or because they support something that belongs to us, or is aligned to our self-interests. That they are associated with us. We have to let them go. We have to stop clinging to them. They are not associated with our self. That's the way to end suffering from them.

From MN 1:


  “Here, bhikkhus, an untaught ordinary person, who has no regard for
  noble ones and is unskilled and undisciplined in their Dhamma, who has
  no regard for true men and is unskilled and undisciplined in their
  Dhamma, perceives earth as earth. Having perceived earth as earth, he
  conceives himself as earth, he conceives himself in earth, he
  conceives himself apart from earth, he conceives earth to be ‘mine,’
  he delights in earth. Why is that? Because he has not fully understood
  it, I say.
  
  “Bhikkhus, a bhikkhu who is an arahant with taints destroyed, who has
  lived the holy life, done what had to be done, laid down the burden,
  reached his own goal, destroyed the fetters of being, and is
  completely liberated through final knowledge, he too directly knows
  earth as earth. Having directly known earth as earth, he does not
  conceive himself as earth, he does not conceive himself in earth, he
  does not conceive himself apart from earth, he does not conceive earth
  to be ‘mine,’ he does not delight in earth. Why is that? Because he
  has fully understood it, I say.


Here, earth is just an example. It can be any theme. Any theme is a mental fabrication. The sutta has many more such themes including unity and disunity, and things which are heard or seen or cognized. One should see the theme as-it-is. He should not form associations between his self and the theme.

In AN 10.96, Ananda knew this very well, when he said to another:


  "'The cosmos is eternal. Only this is true; anything otherwise is
  worthless,' is a viewpoint. 'The cosmos is not eternal... The cosmos
  is finite... The cosmos is infinite... The soul &amp; the body are the
  same... The soul is one thing and the body another... After death a
  Tathagata exists... After death a Tathagata does not exist... After
  death a Tathagata both does &amp; does not exist... After death a
  Tathagata neither does nor does not exist. Only this is true; anything
  otherwise is worthless,' is a viewpoint. The extent to which there are
  viewpoints, view-stances, the taking up of views, obsessions of views,
  the cause of views, &amp; the uprooting of views: that's what I know.
  That's what I see. Knowing that, I say 'I know.' Seeing that, I say 'I
  see.' Why should I say 'I don't know, I don't see'? I do know. I do
  see."


Ananda did take up any of those viewpoints. Instead he knows how one can become obsessed with them and how to remove those obsessions. He does not cling to those views. He does not associate his self with those views.

EDIT:

From Sutta Nipata 4.14:


  "I ask the kinsman of the Sun, the great seer,
  about seclusion &amp; the state of peace.
  Seeing in what way is a monk unbound,
  clinging to nothing in the world?"
  "He should put an entire stop
  to the root of objectification-classifications (papañca):
  'I am the thinker.'
  
  Commentary (Thanissaro):
  On objectification-classifications and their
  role in leading to conflict, see Sn 4.11 and the introduction to
  MN 18. The perception, "I am the thinker" lies at the root of
  these classifications in that it reads into the immediate present a
  set of distinctions — I/not-I; being/not-being; thinker/thought;
  identity/non-identity — that then can proliferate into mental and
  physical conflict. The conceit inherent in this perception thus forms
  a fetter on the mind. To become unbound, one must learn to examine
  these distinctions — which we all take for granted — to see that they
  are simply assumptions that are not inherent in experience, and that
  we would be better off to be able to drop them.