How does a non-native wearing a costume dehumanise real natives? How is it a statement that Native Americans are less human than non-natives? To show a distinction between peoples is not an act of racism in itself. I'll stipulate that "white settlers" did believe American Indians to be "subhuman" in the past. Are you saying that by dressing up in an 'Indian' costume, that is what I believe and am promoting? Are you saying when anyone sees a non-native in costume they think it's okay to kill you?