I vote stay, since a forum is ultimately for the discussion of varied ideas, rather than a one-sided masturbatory opinionfest. You may not agree with what he posts, but you're always welcome to debate his opinions.

It might help your case if you listed/crosslinked your greivances against this person and consolidated them in this thread, It might actually give this thread a reason for existing. Let's dissect this person's personality before you try to tear him apart.