He details numerous psychological experiments in which ordinary people become sadistic.

Hate is perhaps only a mechanism for heightening the us vs. them tribal group-think.

My take from reading these was the Nazis did not find the Josef Mengele’s by picking names at random from the Berlin Medical Society roster. Nor did they take doctors and simply point guns at their heads and say “experiment on Jews”. Too many would have said “nein” and if you executed them, you wouldn’t have doctors.

Herodotus noticed something similar traveling through Babylonia. Enough “eye for an eye”, and the docs decided on another line of work. Herodotus found the Babylonians lining up their sick on the market square, soliciting diagnoses from passers-by.

Of interest, in the Nazi society where such experiments were taking place, animal vivisection was illegal under Nazi law. Proctor included a Nazi era cartoon with a bunch of animals doing the stiff-arm salute to the Nazis for passing that law.

Sort of “groupthink” writ large. Promoting those who “play ball”, and those who resisted because of moral qualms, were sent to Siberia. Easier to do when all the funding came from one source. He did describe docs who did resist throughout the war. They also had funding that the party could not control.