That's not the trick here. The trick is that the format of his talks - and the typical lack of preparation on the part of the typical college student - prohibits nuanced answers.

The correct answer there (to someone who, unlike me, does not believe in objective morality) is something like "I oppose everything Hitler did and stood for. Notwithstanding that, your question is incoherent." What unprepared 20 year old comes up with that on the spot? Much less be prepared to back it up, only in sound bites (because that's what works in the format)?