The point is that he's a stranger and not a close friend, and we're speaking in public. I understand you're trying to say that there's value in honest feedback. But that's generally when it's real feedback that is actionable or at least constructive, this appears to be an attempt at exaggerated humor without anything of value being imparted. You should consider the fact that he's a real human with real feelings and it's simply rude to be disrespectful to talk to anyone this way.
I doubt OP would ever speak in a business environment this way, and if he did those around him would certainly consider it to be harassment and deeply unprofessional.