The "gun to the head" scenario is largely a myth.
Just yesterday I was listening to a radio story about nurses who worked killing handicapped people. It was clear that they were not forced to work in that job and could be transferred to other hospitals without penalty.
Most of the nurses were women. Few were ever prosecuted because many people refused to believe that a woman would participate in such atrocities. Evne those who were convicted were often let out after serving a fraction of their sentence.
However it is clear the German people were intensely indoctrinated into the Nazi philosophy, many from childhood, before it ramped up to extreme levels during the war.
The most interesting point was made by the woman who researched this history. She would like to think that she would have stood up against it if she had been in the situation but never having been there she really didn't know for sure.