While I agree that being an asshole is more frequently harmful than helpful, I don't think the behaviour in question here is actually assholic in nature. Every community needs to have a way of enforcing community values or that community will dissolve. That enforcement can be a police officer, a drill sergeant, a moderator, or just a loud mouthed member of the community that expresses the group's scorn for the behaviour in question.

What is important is that everyone who witnesses the policeman deliver a lecture to delinquent teens, the sergeant chew out a new recruit, the moderator remove a troll or flamebait, or the loud mouth deliver an invective laced screed to the newbie who just doesn't get it, gets the message that "certain behaviours aren't tolerated here" and by extension, other (more polite) behaviours are.

When the policeman gives you the nod on the street corner on your way to work, when the sergeant says, "Nice work", when the moderator uses something you wrote as an example of what a good post looks like, or when the community loudmouth bastard says "SHUT UP AND PAY ATTENTION TO HIM" and you realize he's talking about you - that's the point when you realize you're part of the community.