Which is why I put in that caveat about knowing your players...even with Nazis.
I had the pleasure of gaming with 2 different Jewish gamers in supers games that featured Nazi or neo-Nazi villains. Both had relatives who were survivors. One guy took to it like a duck to water, getting jazzed about classic golden age, 4-color Nazi-busting. The other had to take a hiatus from the group because he kept getting agitated- it dredged up memories of his grandmother's stories. A single neo-Nazi villain was OK, but a Boys from Brazil-esque storyline was too much. (The GM cut that story arc shorter than he had intended once he realized what was going on.)
I've run into stuff like this in a lot of campaigns- homosexual PCs or NPCs, racism, religious fanatic types in modern games, etc.- game long enough and you'll see someone's feelings get hurt.
Heck, I know GMs who get antsy if you play a PC of a different gender than your own. REALLY antsy.