Revenge is personal.

All we ever heard in the films is that the Jedi and Sith don't like each other. Is simply killing each other revenge? Revenge for what?

I don't buy "self defense" either, he could've used force pushes or mindtricks. No need to choke people. Luke isn't bound by the same dogmatic rules as the old Jedi anymore, he kind of just does what makes sense to him.

We know the Sith had the Jedi killed, taking revenge for that makes sense.

It is never mentioned in the films why the Sith disappeared, so why would it be revenge?

Anyway, we had this discussion before, les goûts et les couleurs...

I'm not sure I would have bothered watching The Bangs Of The Sith.