Tom,
I doubt FL was convinced that Germans were evil as propaganda made them out to be. Both Frank's and Joe's ancestry was German. JW was actually detained before arriving in France, if I recall correctly.
If you believe Hartney (truth of which is speculative) the fact these two young men were not of "English" blood made them outcasts and fueled their commitment to prove themselves. In "Up and at 'Em", HH's description of FL's personna; the realization of the futility of this war, was a partial factor in molding Frank into the man he became in the end. His life until then was spent in an environment in total juxtaposition to this strange surreal moonscape full of death and destruction.
Frank Luke was a tragic character but unfortunately America/Hollywood chose to idolize another hero from the Great War (Sgt. York), and without the popularization by a fine actor such as Gary Cooper; his legend quickly faded. I can only hope that someday soon, this will be rectified, and finally he will take his place alongside the great tragic American heros of the 20th century. A story as diverse and unique as those told of Casey Jones, Shoeless Joe Jackson, and the crew of the Challanger.
VBR
Ro§bud