most of the cogs in Hitler's murder machinery were ordinary people not monsters. They went home each night and were hugged by their little young daughter in her dress and clutching her teddy bear... that's part of why a lot of people don't want to face that part of it.
torturers in today's China, Burma and Hun Sen's Cambodia etc. are also ordinary people doing their job. The banality of evil is far scarier than any Freddy Krueger.
It's why William March's fictional creation Rhoda Penmark is so powerful, as, aside from murdering people, she's a perfectly normal obedient and respectful young lady of the mid 1950s.