MMORPGs: When getting your way is not enough; PvP

What's wrong with MMOs is often discussed. Some say it has to do with the structure of the game, others say it has to do with the entire community, and others say some aren't social enough. The truth to it, however, is that what truly ruins the experience in an MMO are the sore losers, and the majority of those sore losers are heavily involved with PvP. Of course, why wouldn't they be; what other aspect of the game is there an outlet that encourages you to be a tremendous douche as part of the experience?