If showing him the May-June numbers ($35k drop in condo median in a single month) doesn’t make him at least do a little of his own research first, I wouldn’t bother. You tried several times, so he won’t be able to fault you in a few years when he’s kicking himself.

I have several acquaintances who bought at the peak and have since lost everything. I tried to talk them out of it at the time, but you have to keep in mind that people have been brainwashed for years by the media and people they still think are experts (RE agents). If he’s going to open houses, those agents are only reinforcing his programming (and they can be VERY convincing) that NOW is the time to buy, so a 10-minute debate with you isn’t going to do it.