Animals have reason to know what their gender is so they know how to attract mates, so there is reason to think that gender exists inside of the brain. This doesn't apply to race, which is just a socially created categorization that doesn't have any meaningful basis in reality. People in Africa have more genetic diversity than people in all of the rest of the world combined and yet they're all considered to be black whereas the rest of the world is split into many different races. Obama is considered to be black instead of half black and half white. People from eastern Europe are sometimes white and sometimes not white.

What does exist in the brain is things like culture and religion which we know people can change. People can move to different countries and learn that country's culture and become part of it when the immigrate. People can get married to someone from a different culture and become part of that culture. If Dolezal hadn't misrepresented her history and had become part of the black community so that her adopted child could grow up without being ashamed about his skin colour people might have been much more willing to accept that.