I think unfortunately, in this particular case, you can't fix what seems to be the single biggest problem--- one person who is already widely condemned, banned from forums/IRC when people see him, but nonetheless persists, and keeps reappearing in new guises.
I can imagine fixing the more common problems, like pervasive stupid sexist comments everywhere, and inappropriate content in conference presentations, but stamping out every single rare-but-extant crazy stalker seems unlikely. A number of high-profile bloggers, Usenet posters, and forum admins of both genders have attracted unhinged people of that sort, and discussion about what to do about the problem dates back at least 20 years.