Notion of good and bad in Buddhism if I understand correctly, Buddhism is opposed to dualistic concepts: Us vs. them, beautiful vs. ugly, pain vs. pleasure. We should rather realise the emptiness of those constructs in order to see the things in the way they really are, i.e. see their real nature.

How then, does that translate to the concept of good and bad? Because I think every Buddhist tradition teaches us that certain behaviours, acts or ways of thinking are beneficial and create good karma, whereas others are detrimental to our spiritual progress or to our own well-being and that of others and create bad karma. Examples of good vs. bad behaviour abound in many texts like the Vinaya rules but also in the Noble Eightfold Path itself. Right speech for example is considered good whereas the opposite - lying, denouncing, spreading rumors, careless speech in general are surely to be considered bad, detrimental, whatever you want to call it.

How can I accept the duality of good vs. bad while accepting that other dualities are just hollow projections of the untrained layman's mind that keep me from seeing the true nature of things?

I would also be greatly interested if somebody could shed a light on the different traditions' views on the subject.

Thank you!
The original Buddhist teachings do not include a doctrine of non-duality. The Buddha's enlightenment came from ending craving &amp; attachment rather than from ending dualistic perceptions &amp; thoughts.

Understanding good &amp; bad for moral/social purposes is one kind of knowledge. 

Seeing &amp; understanding the true nature of reality for liberation is another kind of knowledge. 

The Buddha taught: (1) avoid evil; (2) do good; &amp; (3) purify the mind. Purifying the mind means ending egotistic attachment towards good &amp; bad rather than giving up the understanding of good &amp; bad.


  'See evil as evil.' This is the first Dhamma discourse. 'Having seen evil as evil, become disenchanted there, dispassionate there,
  released.' This is the second Dhamma discourse. These are the two
  Dhamma discourses that the Tathagata — worthy &amp; rightly self-awakened
  — has given in sequence.
  
  Itivuttaka 39