I think the slam was intended for "hispanic veterans" who are indignant about Burns failure to insert policical correctness into a documentary.
I haven't seen the documentary yet of course, but in my opinion the only valid focus on ethnicity in a history of Americans in WWII would be on the institutional segregation of black Americans, and the story of the American Indian code talkers, and the Japanese Neisi. It has some relevance in those cases.
I have Mexican blood, and a Mexican great uncle who fought at Tarawa. I know he would have been disgusted at the transparent manner those activists try to inject modern politics into history. He (that great uncle) did by the way tell me often when I was a young boy that he had nothing but contempt for Mexico and wouldn't consider living in that country as a king. He also had a brother (who I never knew) who was severely wounded at the Remagen Bridge.
The travesty of war lies in those who have to live after it's over.