The whole big point of the Holocaust that everyone was supposed to have learned is that not only did one not have to be a "Nazi" (or even particularly sympathize with the regime or its ideology) in order to be an active or passive collaborator.
All you had to do was keep your head down, and do what you were told.
Yes but it would be accruate to describe all US soldiers as defenders of republican democracy, specifically that outlined in the US constitution. Defending the constitution is the heart of the oath. If that constitution was altered, as is can legally be, then all active US soldiers would become supporters of whatever form of government is described therein. Not being a member of a paticular party does not free a soldier from being described as a supporter of the government they serve.
This is not just theoretical. Many US soldiers refused to recognize Obama as legitimate. Those soldiers were shown the door. A similar transition will occur in a few weeks.
It's like saying that CCP soldiers can't be called CCP because they might not necessarily hold communist ideologies themselves.