It happens no matter what you do: you get into a bad group of players, or you and your guild leader (or shell leader, or supergroup leader, or whatever) have a falling-out, or you just tagged something that another person needs. Whatever the reasons, feelings can flare when playing an MMO, and we tend to invest a lot of ourselves in our virtual avatars.
Some people, when confronted with rising tempers, try to get everyone to calm down and even things out. It's not that big of a deal, after all -- it's just a video game, and it's better to make friends than enemies. On the other hand, some people would rather take the chance to hold the moral high ground and lash out where it's appropriate. After all, if you don't tell people what they do wrong, they'll never learn -- and it's just a video game, how could they be so upset when you give them what they have coming?
So which do you generally try to be? When everyone gets touchy, do you try and be the person calming people down, or the one stirring them up? Do you try to convince people to stick with a bad group, or do you let the dead weight know what they're doing wrong and then get the heck out of Dodge?