When I’ve taught ethics in the past, we always discuss the Nazi era. Not because the Nazis acted unethically, but because of how everyone else acted.
For example, we read about the vans that carried Jewish prisoners that had the exhaust system designed to empty into the van. The point is not how awful that is, but that there must have been an engineer somewhere who figured out the best way to design and build such a thing. And that engineer wasn’t a Nazi soldier, he or she was probably no different from anyone else at that time, with kids and a family and friends and so on. Not an evil scientist in a lab, but just a design engineer in a corporation.
One point of the discussion is that “normal” people have acted quite unethically in the past, and how can we prevent that happening to us.
Interesting illustration of mental imagery (from Dennett):
Picture a 3 by 3 grid. Then picture the words “gas”, “oil”, and “dry” spelled downwards in the columns left to right in that order. Looking at the picture in your mind, read the words across on the grid.
I can figure out what the words are of course, but it is very hard for me to read them off the grid. I should be able to if I could actually picture it. It was fascinating for me to think that this isn’t true for everyone.