There are a lot of expectations to MMOs that feature PvP.
And then, as it is an MMO, there is a lot of different people with different backgrounds who bring different opinions as to whats right and whats wrong. This naturally causes conflict for those who has a hard time expressing themselves in a civil manor.
Even those who do act reasonably will inevitably be pested and sink to the same level as those who presented an uncomprehending ignorance to begin with.
Thus we have a, society if you will, that effectively devolves.
This will not change before game developers require consumers to undergo a IQ test in order to purchase the game.