You're 180 degrees off here. The doc wasn't selling the notion that Hitler was a man of peace. It tries to analyze how the Nazi propaganda machine sold the notion of him as one to people who should have known better.
If the doc Hitler is a man of peace, they have to show some evidence that he has been in his life. Right? The statement needs to be backed up. What George S. said is simply an "argument" that holds no water, that is the problem. What many people believed, is not fact.
This ain't no abstract discussion. Hitler was a real man who did real deeds. And most of those deeds were not what people would consider peaceful.
The doc does not try to justify what he did, and many people in the world are okay with what he tried. Mongolians think Genghis Khan is the greatest, despite his brutal acts.