What would you say if you asked,"Are you crazy" and the answer was yes?

I know most here would not ask such a thing, but suppose some stranger did or said something that annoyed you and and you blurted out, “Are you crazy?” and the person very matter of factly answers, “Yes I am.”

That could make for a very surreal conversation.
“You’re kidding, right?”
“No, I have been diagnosed as borderline criminally insane. Yourself?”