It could also be why this is set in WW1, rather than WW2. The first World War was far more morally ambiguous than the second - it was a result of the labyrinthine military and political tactics of several centuries finally coming to a head, and while the Germans were the enemy, the impression I always got was that the majority of them didn't really have the slightest idea why they were actually fighting - the generals said 'fight', so they fought. A WW1 flying ace is far more convincing as an honorable foe than a man working for the Nazis.