The idea that morality is a function of situation more than character is called "situationism" in philosophy, I just looked it up, see [1][2]. Experimental psychology does find that character is fairly weak in most people and that under external pressure people will often behave inhumanely (Stanford prison experiment, Milgram obedience experiment, etc).

I still believe it is important to not be overly cynical. My mental model is that most people are neutral or good. It might be proved wrong say 5% of the time, when people are indeed put in MBS-like position. But the vast majority of the time it will be correct, and it will be much more useful than the cynical model where your normal friends are potential murderers that just lack opportunity. A more correct mental model is not always more useful.

[1] https://en.wikipedia.org/wiki/Situationism_(psychology) [2] https://plato.stanford.edu/entries/moral-character/#MorChaEm...