I don’t think you have to get as extreme as “Nazi” to get that sort of “for the greater good” mindset going. Plenty of history’s “good guys” have done terrible things to people. This isn’t, of course, in any way to say that what the Nazis did was okay (I will never say that because it wasn’t) I’m just saying that a mentality of “it’s for the best, it has to be done” is a far more universal human response than we would feel comfortable in admitting.
A real world example of this is the Milgram experiment where the psychologist Stanley Milgram essentially replicated the mindset that Steve is talking about in ordinary blue collar American men in the fifties. His study has since be replicated a whole bunch of times, all over the world, with men and women of all ages, and the results have remained the same in all cases. You can read in more detail at the wiki link, but essentially what he did was he that he advertised for volunteers to help with an experiment on learning. The volunteers were paired off as “learner” and “teacher” and the experiment was that every time the student remembered something wrong, the teacher would apply stronger and stronger electric shocks. What the volunteers didn’t know was that the “learner” was a plant, and that there were no electric shocks being delivered, and that the actual experiment was about how far people would go with hurting another human being if they believed it was “necessary” - 66% of his volunteers ended up administering what they believed was a 400 volt electric shock to the “learner” who had stopped responding five minutes ago. Kind of a shocking result, that decent, ordinary people can be convinced to do horrible things by the power of “you must, it’s necessary.” I highly recommend reading the wiki link, it’s eye opening reading.
A larp example, I played a character in a horror game who did some pretty horrific things. When I was in character and playing her, I didn’t see these things as horrible, because to the character, they were absolutely necessary to be done. It had to happen. Those people had to die. Those people had to be betrayed. Those people had to be tortured. Coming out of character was a surreal experience, to look back on the weekend from an OOC perspective and realise all the terrible things the character had done, and the fact they didn’t seem so horrific to the character. Out of character, her actions were selfish and heading fast towards psychopathic, and the thing I found fascinating was how natural and necessary they had seemed in character. It was a slightly scary, but really interesting experience.
I think trying out different moral and personal codes is one of the most fascinating things about larping. Boffer combat I can take or leave, it’s the trying other people’s headspace out that really appeals. Really strong IC/OOC boundaries are absolutely necessary though, and I think a high level of maturity on the part of the other roleplayers to understand that while Bob is playing a racist, Bob himself is not actually a racist. Personally, it makes me feel good that this community is in a place where we feel uncomfortable playing things like racism. It’s a good sign about our values, right?