Strange. I had an uncle who was a guard at Camp Attabury. He said most of the Germans there were Lutherans.
I suspect that one of the reasons they picked Atterbury for a POW camp was the fact that there were many folks in the area who spoke German.
I know the SS fomented riot was resolved through the provisioning of the camps with German style bread baked by local women in Columbus and other towns.
Just because a person was a German POW does not mean that he supported or even understood the Nazi party. Pope Benedict XVI is a perfect example. He was drafted. He had no choice. It was not an option to not support the Nazis (the definition of totalitarianism).
I am not a Nazi sympathizer, but I recognize that Hitler's power came from the evil of political leaders, not the evil of the German populace. The populace was led blind to their destruction.