"I think there are people who are interested in what he has to say, it's just that he is so vituperative and redundant in saying it, that he tended to drive any dissenting posters away, leaving just a few eager supporters able to stomach his endless raving. But then, what's the point of a debate where everyone agrees?" (from "A Brief History of Sly's Thread, Part 1")
In lieu of banning him (if he decides to stay) how about this as a "compromise": Address your own "ground swell clamoring" (which you obviously appear to have), and simply advise them to place Sly on ignore, en masse. No engagement, no incitement, end of problem. Those wishing to engage him may do so at their own risk (obviously, there is a desire from elements of both sides to engage in the type of frothy exchange stirred up by Mr. Sly). It is a compromise, but life appears to be full of 'em. C'est la guerre.