a) it has nothing to do with us, he's the scientist who identified one big wrinkle in a giant quilt we all occupy
b) to be a working professional in Nazi Germany meant being a Nazi. It was designed that way.
c) He was no humanitarian, but he was no Dr. Mengele, either
If I may shed a bit of light on this from my study of the years before the rise of Hitler: this was a incredibly authoritarian society even before it went Nazi. And incredibly anti-Semitic... which was the norm for most of Europe, frankly, but devastating lost wars and a crumbling empire had made Germans frantic for a scapegoat they could blame.
Popular child rearing manuals of the early twentieth century in Germany emphasized the child's obedience and routine, reinforced with deprivation, shaming, and outright violence. They advocated tying children to their beds lest they masturbate, and they had rigs to make them sit up straight and hand devices to make them write neatly. They were overwhelmingly raised authoritarian and they "obeyed orders," as we all know.
Under such circumstances, a giant slice of the population were helpless to develop their individuality or personal ethics. And there were few competing systems they could follow, instead: communism was actually popular because it was actually more empowering for women and minorities than the existing structure, but Hitler killed as many as he could round up.
And think about that for a bit; your neighborhood, your job, your friends; it was obey or get evicted, fired, and shunned. This was before the death threats started being carried out; now think about resisting when the police drag you away as a result... and no one comes back.
It's daunting, to say the least.