First off because unlike some players the imm staff holds inself to fairly high standards when it comes to how they interact with players. And for better or worse being a douche of a person is not in and of itself against the rules.

Second he would just roll up something else and continue his schtick, it's not like he isn't consistent.

And if they banned him he would just use a rotating series of Proxies and do his hardest to ruin as many peoples experiences as possible both in game and out because he is that immature.

To be honest if he didn't have a leader spot or any kind of communication ability he would be an exciting player to play with/against but those avenues bring out the douche.