WoW is at fault for the general degradation of kindness within the PC gaming community as a whole, WoW players aren't really much different than the little kids on xbox live who squeal in anger when they dont get their way and scream obscenities through their mics.
The WoW playerbase being the cancer it became, spreads to every game it can, older games manage to oust those types of players and thier attitudes thanks in part to already well established gaming communities.
The degradation of a community starts when a developer becomes complacent and a games population grows out of control and that developer is not willing or able to police the behavior that goes on. Frankly I don't think until WoW finally dies(heres hoping) and that generation of gamers who became so unkind thanks to that games atmosphere either grow up or quit playing MMOs will a new MMO be able to launch without being infected by the cretins who call themselves current, or former WoW players.