Thing is, as you have pointed out, humans do have biases. Of course, they can discard them, but it is just a can and throughout history, it didn't happen until the 20th century. That's why I do not understand why many people think that racism or sexism could have been avoided by a magical point of divergence where after some centuries world peace reigned and we all lived in harmony. There are always some people out there thinking that racism is justified, who think homosexuals are morally disgusting or that think that women belong to the kitchen. I would even go as far as to say that racism and sexism are indeed inevitable, simply because the bias against one group or another has existed throughout millennia in very different cultures. Humans are just humans, we never liked foreigners at first, and it's just too easy to politically or economically capitalize on this resentment. And on the difference between woman and men, of course they are equal but still different. Just like cultures are equal, but different. And this difference is enough to develop some bias against the other side. Sexism will always develop, especially because men are stronger and more aggressive, also men do not have to go through the pain of having a child in their womb for nine months which more oftenly than not forces woman to retire until the birth of the child, forcing their husbands or boyfriends to care for and protect her and their shared child, therefore enabling some sort of patriarchy and "supremacy" over woman. Not that it is justified to establish one because it is not, but I just want to explain why women played an "inferior" role in politics and common life for most of human civilization.