They might actually be a bit stupid, but maybe they'll do it if you tell them it's because you are worried that you would fall for a scammer impersonating them. That at least would let them keep their stupid pride.

The article makes a point of explaining how the world-renowned expert on identifying deepfake scams can no longer pass his own tests.

If an expert can't distinguish, it has absolutely nothing to do with being "stupid" or not. So send them that, maybe.

If they are still stubborn about it, then thank them for contributing to the future funding of Scam the World With AI.

You don’t even need this. You just ask “what did we do last Tuesday”. A scammer will hang up, even if the actual answer is “I haven’t seen you in two years”.