Oh, I'm well aware that this technique could be used to spread irrational and harmful memes. But if you're trying to persuade someone to rationality using techniques of argument which presume rationality, it's unlikely that you'll succeed. So you may have to get your rationalist hands dirty.

Your call on what's the better outcome: successfully convincing someone to be more rational (but having their agency violated through irrational persuasion) or leaving that person in the dark. It's a nontrivial moral dilemma which should only be considered once rational persuasion has failed.