On another board, when we had a troll who was clearly attempting to start a food fight (and would, when called on garbage, try to slide into a different argument to divert attention from his foolishness) -- we simply posted "please don't feed the troll." When people stop replying to them, typically they get crazier and crazier in their posts so that everyone understands what their real agenda is.

I suggest that is probably the best course of action with this one.