A lot of men believed they were fighting for their country. All the atrocities known to us are well known because hindsight is 20/20. When you're 16 and you're drafted into combat because the "UK, France, and Russia declared war on you", you're going to fight tooth and nail for the country you believe in. I believe in these mens belief that they think the Wehrmacht didn't do anything. They fought toe to toe with brothers and friends for what seemed to be a noble cause. To them the enemy wasnt the Wehrmacht as it was to citizens, it was the allied powers. That also comes as a benefit to how Riddler was exceptionally powerful with words and propaganda. That is the whole point anyways, to convince people. They also didn't really have a choice either. Orders are orders and they have to follow them.
Now, WWII is the most unique taboo subject in Germany. Such an atrocity it must not be spoken of.
I have little doubt that these men who fought in the war were able to get a hold of all the information that WWII grants us on this massive scale, esp. in the european front. For these men to hear about this, it probably comes as a great shock, maybe even an insult to the fact that they put their lives on the front line.
Remember, there is a huge difference between an SS Soldier and a man who was pulled from home to fight in a war he had no choice in fighting.
