What's the point of an MMO where everyone is nice to each other again?
No competition = no fun
Gotta have some rivalries.
And... spoken like a villain. Showing the difference between players who prefer pvp and those who prefer co-op, where helping each other do something is more rewarding.
Here's a sample test.
Someone in the chat lobby says 'anyone want to join with me, I'm having a hard time getting something done.'
If your response is, 'I'll help you, nice to meet someone and help', you're co-op.
If your response is 'lol, I hope I see you on the other team and get to farm you', you're villain.
Of course there is room for rivalries - but are they part of the game, or are they the only point of the game?
Second test:
The match is over. The game allows the other team to collect more rewards, but you can prevent it.
Do you say 'let them get rewards, we're all players'? That's co-op.
Or do you say 'lol, screw them', and prevent them getting rewards just to ruin their day?
I know I'm getting close to treating pvp and griefing similarly, and they're not the same.
When I say villain, I mean more griefing type attitude.
That's why I don't say he's a villain for 'killing rival clan members'.
It's the people who think it's fun to 'camp new players' who are the villain types I'm talking about.
I've sometimes denied the other team rewards - but not really enjoyed that part of it. It was more like 'the game put this in so what the heck, play it as designed', but usually I don't.