So, let me see if I've got this. You attempted to conduct a logical, informed and intelligent discussion with a fool and he responded in an illogical manner?
There's a difference between ignorance and intentional stupidity. One is due to a lack of knowledge and experience and the other is due to self-centered arrogance. Willful stupidity thrives on attention, even the negative variety. You can't fix stupid, but you can starve it. Ignore it long enough, and it will wander into the street where it will encounter natural consequences.
I'm sure your concern is not for educating this person, but is instead for setting the record straight for those he might confuse. I think all you can do is state the facts, drop the mic, and walk off stage.