Why do MMORPG communities always suck?

I have played EVERY single popular MMO known to man (both free and pay-to-play) and not one of them had a decent community. I remember playing this one small MMO which had only had a few hundred players and it was alright for a while, but once the game was advertised more, then a lot of shitty people came and ruined it. Why?

i played WOW on my friends account and i was talking to these people... they couldnt get a joke. i did my araibian voice and they were bitching about it being offensive... along with every other thing i said. so i came to the conclusion that pretty much everyone that plays an mmorpg has an electric bug up their ass that tells people what to say when they are trying to censor something... just like those commies. DAMN COMMIES!