People are people. A lot of people take their real-life frustrations out via the game, which isn't right.
A lot of people have nobody to vent to outside of the game, or anyone to yell at or belittle, so they
do it from the comfort of their computer chair because really, besides being reported, there's no risk
of punishment or repercussion for them.

And honestly, some people play MMOs for the sole purpose to belittle people. They get kicks out of it.
I wouldn't let it get to you. Like wildgalax said, just find the right crowd and you can enjoy the game.