The only thing I can bring in to counter this, is that if anything, you should blame Itachi for how he's acting - after all, it was he who shaped and twisted Sasuke's personality with what he did. Can you just imagine even a splinter of the trauma he went through? Everyone you cared for, murdered by the one you looked up to the most; that screws with your head, and as if the massacre wasn't enough, a few years later he shows up again and f*cks with Sasuke even more after that, calling him weak and turning him to an even darker path. Sasuke, at that point, had barely anything left. His whole life and purpose had been shaped and fixated on destroying Itachi. Then he finds out the truth. Giant mindf*ck right there. That's where a lot of his personality comes from.
In the end, I can't tell you not to dislike him because, hey, there's always someone with that one quality that just pisses you off for some reason, but at least try to understand him.
Funny thing is I don't even really like him that much. I do like him somewhat, and I just think his character development is fascinating from a psychological perspective.
For most other people, I'd assume it's because despite going through all of the things I mentioned above, he still finds a way to get through it and complete his goals. He doesn't just talk shit, he delivers as well.