I think I have come up with a way to make the themes interesting to them. As they already love Harry Potter, they're not afraid to use complicated Latin phrases. So I can say something like, "The key to casting a successful Modus Ponens spell is to first summon the Antecedens and then proceed to the Consequens. Never summon Consequens first, as it will cause the spell to blow up in your face." Then we can study some defensive techniques against the Ad Hominem curse.