Everyone likes what they like. Some people hate Horde some people hate Alliance. Some people like to pretend to hate the other faction for RP purposes but in reality realize that we all play the same game.
For example, I don’t actually think Alliance players are the scum of the earth genocidal racists, or that Garrosh was actually the best leader the Horde ever had. But it’s so much more fun to RP that way to get that little bit more from the experience.
All in all I think that 95% of Alli players are stand up people who enjoy the same game I do (Then there are the people who camp The Maw, but both sides pull that kind of crap). However, I could never play Alliance because I find their Goody Two-shoes demeanor and European Castle aesthetic to be so boring.