Regardless of whether you "know a little bit about" the position of assuming that Germans who went along with the Nazi regime were a priori evil, you seem to be maintaining that as your argument. I cannot support that.
This is my third comment, and it's the third time that I'm telling you that it's not my position that people are good or evil. People do good or do evil, they don't
become good or evil.
If you become evil, you're no longer responsible for your actions. That's why Stangl made this argument. He wanted to say that anyone could have done this. I don't think that's true. He decided to kill people. He was not morally deadened or amoral, or he wouldn't have tried to justify himself in this way.
Your examples from the US are entirely compelling. The people convicted for implementing government policy to torture prisoners at Abu Ghraib were, as Stangl tried to assert he was, compelled by their social context to follow orders. There is recognition under law of some culpability in soldiers who follow immoral orders, though most countries understand that culpability to be limited. (Which is largely the result of public reaction to post WWII trials.)
Here in the US, there has been political agitation to hold the people who issued the orders accountable for their crimes, to close the black sites, to close Guantanamo and Bagram. Some of that political movement has come from within our military.
If I had to compare Stangl's role to anyone's role in the unfolding torture scandal in the US, I would compare him to the psychologists who pushed for the SERE program to be turned into a training program for torturers. In both cases, people lent their technical expertise to harming people. Stangl knew that he was going to be killing people in large numbers, and he understood that this was wrong. The psychologists in this case were aware that the scientific consensus was against the efficacy of torture as means of collecting intelligence. Currently, some of these psychologists are arguing that they felt pressure from the post-9/11, War on Terror context.
You would not, if you were an army psychologist, have argued in favor of creating a program to torture prisoners. You just wouldn't. It's not because you are a good person and they are bad people. It's because it takes an active moral choice to do the wrong thing. It would have been very difficult for the soldiers who were prosecuted for the Abu Ghraib discoveries to have refused their orders. (Though someone had to have the courage to leak the information that it was happening to cause the scandal in the first place.)