This was the claim. And I refuse this notion. The worst atrocities humans inflicted upon one another were derived from a fundamental belief that the "others" being oppressed were meaningfully different from the oppressors, and therefore was ok to oppress them.
And about people treating you differently based on their perception of you, that is a different claim. And that is just basic human nature. Everyone (man or woman, white or black) judges based on appearances, especially when that is the first (and sometimes only) information you have to navigate.