As far as #2, they are still people, no matter how authoritarian/establishmentarian, so they still need to convince themselves (and each-other) that what they're doing is right (even though, seemingly, the bar for achieving that may be lower than for a typical person).

At the risk of violating some internet law, the people (they were still people) of Nazi Germany convinced themselves and each other to commit mass evil, or at least to go with the flow and not rise up against it.

The people of Nazi Germany were not special, they were no different than any other group of people.

We are all our own worst danger. When we restrain our government through laws and constitutions, it's not to protect ourselves from some "other," it's to protect ourselves from ourselves.

You could always not bring up Nazi and just use the Milgram experiment: http://en.wikipedia.org/wiki/Milgram_experiment

Besides the Milgram experiment, Soloman Asch's conformity experiments, Zombardo's Stanford Prison study, the innocent bystander and the fundamental attribution error should all be required for politicians writing laws, police enforcing them, prosecutors bringing charges against people using them and judges meting out the final judgement. Possibly even jurors should be required to learn about those basic psychological principles before sitting in on a trial. You could cover all of them for the jurors in 2 days I reckon.

Or better yet, mention both.

Rendering certain segments of history taboo is a great way to fail to learn from them.