Rob stated for the record:
The advantage to banning him now is that it prevents subtle skewing of articles or skewing of articles on obscure topics, both which may go unnoticed and uncorrected. It also saves a lot of stress and sweat for those editors who have to deal with him until he inevitably gets banned for something. Neither of these will be that detrimental to the project as a whole in the long run, but they are not negligible effects.
Yeah, there's no need to wait for him to do anything wrong. He should be banned because he might do something wrong at some indefinite point in the future. After all, we don't choose who can work on this project based on anything trivial like their behaviors, we choose them based on what we think they believe.
And just to put a juicy sweet cherry on top of this sundae of summary justice, our precognition is infallible, so we're sure that he will "inevitably get banned for something."
With all that righteousness on our side, who could possibly want to waste time on archaic betises like formal charges, due process, the right to confront one's accuser, and similar nonsense?
After all, giving the accused his "day in court" would distinguish us from various disgusting people, like, oh, say, the Nazis.