I agree, this kind of thing is unacceptable, unpleasant and just downright rude. And even if people aren't outright abusing each other there's still a depressing amount of posters bitching and taking pot shots at other fans. I mean, for Pete's sake, we're all supposed to be on the same side, aren't we??
I think Ronnyc's idea about having to earn posting privileges is a good one. It might help people to learn to actually think before posting nonsense. I would also favour stricter moderation, maybe restricting the troublemakers to a "quarantine" area for a while, or having a "three strikes and you're out" policy. I miss the community atmosphere we used to have and I'd be happy to get it back, even if it meant a tightening of the rules.