Why did that turn him on?

I don't get it? Why would you want someone to say, "N**G*R *beep* Me Hard!" repeatedly? Was her trying to get her true, repressed feelings out of her or something or was it just to shock the audience to see this large, dark black man and skinny, flat young white girl? Honestly I don't think it was rape. She might have had second thoughts for a moment, but in the end she stayed. He didn't force her...physically anyway.