Jeremy -- count me in on you and Dave's approach. It's the only reason why I even bother (occasionally!) to let myself get dragged down argumentative rabbit-holes on Facebook walls (usually those belonging to friends, where I get into it with THEIR friends who are complete stranger to me personally).

I'm never under the delusion that I'll actually be able to change the mind of a sparring partner who's digging in his/her heels. My tactic is solely for the benefit of the observers within the peanut gallery, to encourage them to empower themselves and stand up to bullies. And, as you'd also mentioned, sometimes getting into that heated argument will help me to self-examine other angles on the subject that I might not have considered before.

I always say: I don't *LIKE* to argue -- but I'm damn good at it! :-P