Strangely enough The Strain (a show about vampires) portrayed it very well.
If you were “useful” you could basically sell your soul and help with some part of the extermination of people just like you. When you stopped helping you were killed and replaced.
Modern republicans ignore every subtlety and act like some of them were treated like humans and implying the reason everyone else was brutally executed was because they were worthless.
It’s because a lot of modern republicans openly identify with nazis these days.