How do you explain prejudice to someone who's never seen it before? How do you explain that so many people hate simply because of color, or gender, or the goings-on inside one's mind? How do you explain thousands of years of rage and fighting to someone who can't comprehend why such things would happen? How do you explain female circumcision, the slave trade, religious oppression?
How can you explain an entire history of prejudice when you don't understand it yourself?