Question: Let us start with a simple sentence:

* Ich **lerne** Deutsch.

... in which we have Subject + Verb + Object. Then we have:

* Du musst **lernen**, den Ball weiter zu werfen.

... in which we replace the Object with the phrase "*den Ball weiter zu werfen*".

By the same logic, I first have:

* Ich **hasse** Fast-Food.

But then we need "es" here (like a dummy object):

* Ich **hasse** *es*, ausgelacht zu werden.

### My questions:

1. Can I just say "Ich **hasse**, ausgelacht zu werden." and it is still grammatically correct?
2. I have never seen "Du musst *es* lernen, den Ball weiter zu werfen." But "hassen" and "lernen" are verbs that accept a direct object. So they could function *in the same way*. Is it correct?
3. Interestingly, I found both examples of "hassen" with ([link](http://www.d-seite.de/vis/vis.php?lemma=hassen)) and without "es" ([link](https://www.youtube.com/watch?v=8ZmGjh8qrZg)). So both are ok?

Answer: 
In my experience (both as a language learner and language teacher), attempting to understand grammar is not usually a helpful approach to learning a language.

Look at how children learn their mother tongue. Most native speakers do not understand the grammatical rules of their native tongue (at least not until they are forced to learn them in school), and yet most of them speak their native tongue at the proficiency level of a native speaker ;-)

So how do they do it? They do two things: Consume lots of examples of that language (by listening to or reading other native speakers), and they emulate what they hear and read, until they develop a **feeling for the language**.

Learning grammar is an approach that does not help you develop a feel feeling for a language. Instead what you learn is to construct sentences by following rules. But that is not how languages work. Languages are both more complex than the grammatical rules that language teachers work with and more flexible than (traditional) grammar. Most speakers do not speak "correctly" most of the time, but what they speak is nevertheless correct and proper and unremarkable to most other speakers.

I would therefore recommend, that you don't try to understand why *hassen* may or may not need an object, but rather watch a lot of movies in German (with subtitles, if they help you), read lots of books in German, and, if you can, talk to lots of Germans and write lots of German text, i.e. actively produce language.

And it doesn't matter if you make mistakes. You will be understood, and sometimes corrected, and eventually you will outgrow your mistakes in the same way that you outgrew them in your native tongue. And if you keep making some few mistakes, don't worry. All native speakers do.

Just have fun.
Let me give you an answer based solely on gut feeling.

My impression is that the subtlety of whether to use "es" or not is related to the pronunciation. Note that "hasse" ends with the vowel e and "es" begins with the same vowel. This means that in spoken language the two words melt together. The sentence "Ich hasse es, ausgelacht zu werden" sounds like "Ich hasse's, ausgelacht zu werden". This melting effect seems to me so convenient/pleasant that in practice "es" is used after "hasse" whenever grammatically possible.

For verbs thay don't end on e, where no melting is possible, inserting the "es" does seem less common to me: "Ich mag, ausgelacht zu werden" is something I'd say. On the other hand, "Ich liebe es, ausgelacht zu werden" requires again the "es" which in this case melts together in spoken language to something like "Ich liebes, ausgelacht zu werden".

The example "Ich versuche, eine gute Note zu erhalten" from johni's answer is also interesting from this point of view. Here I'd say that "es" is omitted because "eine" melts together with "versuche" even better than "es". The sentence sounds like "Ich versucheine gute Note zu erhalten". Replacing "eine" by a word that does not begin with e or ei makes inserting "es" feel less inappropriate: "Ich versuche es, Informationen zu erhalten". However, I do agree that with "versuche" the omission of "es" is always preferred. I'd explain this difference to "hasse" with the fact that the short form "Ich versuch' " is more formal than "Ich hass' ". Therefore, "Ich versuche" can melt together more easily also with words that begin with vowels: "Ich versuche, an Informationen zu kommen" sounds like "Ich versuch', an Informationen zu kommen" which is always ok and appropriate. In contrast, "Ich hass' " is usually used only in a very emotional, informal context: "Ich hass' dich!", "Ich hass' meine Eltern!", "Ich hass' euch alle, ihr XXX!". Saying something like "Ich hasse, an diesen ständigen Meetings teilzunehmen" is therefore less common than "Ich hasse es, an diesen ständigen Meetings teilzunehmen" because the former sounds like "Ich hass', an diesen Meetings teilzunehmen..." which is something a 15 year-old student might perhaps say in school to his friends but not an adult in a professional context - not even when losing temper.