If everyone always agreed, this wouldn't be much of a site. Disagreements often make for the best discussions/threads. Everyone just needs to be smart and respectful (I realize the former may be hard for some) in their posts. I don't think it's too hard.
One thing that absolutely drives me nuts are internet tough guys. Anyone who can get personally insulting- calling people douche bags, physical threats, etc on a fan website or any other online forum is a complete tool. It's really easy to hide behind a user name and an avatar and go after others. It's also really cowardly and childish. Anyone remember that Porterhouse fiasco??
Don't be dumb, don't be a bully. Or I'll kick your ass!