It's not interesting! If you argue I should light my pants on fire, or shoot myself out of a canon, or dunk my head in tar bucket, what am I supposed to respond with?

"That's nuts!"

It's not a lack of curiosity, the position the opponent is arguing doesn't have legs and that's readily apparent.

"Renounce your sinful ways of sewing machines and egg beaters! RETVRN TO TRADITION!"

Like, what? That doesn't deserve a dignified response, there's no argument there. If anything, engaging grants it a kind of credibility that is more harmful than just saying "Move along sweetie, leave the crazy man be".