Well, I'm no expert, but I'm pretty sure ganging up on a guy will make him care less about the content of his posts and make him become even more of a douche since it doesn't look like anyone likes him already. He was Banned, got pissed, and pissed other people off. He did his time, comes back, and everyones pushing him BACK into the behaviour that they disliked so much. That's obviously going to cause even bigger problems and all likelyness a perma-Ban on a guy who deosn't fully deserve it. The first thing you guys do when he gets back is say you're no longer friends and Image fail. What type of community is that. Trekster got the idea right, maybe some of you to should too.
And like I said, he's 14. He's obviously going to be immature. That's why you guide him and show him the ropes about proper online etiquete. You don't further provoke him.