We do not hate people for being different from us. We hate people because we see too much of ourselves in them. 
After initially denying this, I have come to see it as a truth. There is only one person I truly hate, and I realize that we share the same character traits. I have the potential to be exactly who she is and to be exactly what she was to me. It is that potential in myself that scares me. There are times that I recognize that I am acting like her and I am horrified.
Or as Rashi would say, "Mum she'bcha..."
The flaw that is in your friend is truly in you.
 I realize this is a very broad statement. You can effectively argue that we hate people because we do not understand them ("Mob Song" in Beauty and the Beast, one of my favorites) or that hate is engineered as a social mechanism by a political power. I agree that this is all true. But on the most basic level of all, I think hatred stems from the realization that we are the same. We struggle to create difference where there is none. We cannot forgive the person for being so akin to us, so alike, because we are horrified by what we see them do, what we have the potential to do- what we perhaps have done.