Black-on-white crime is much higher than white-on-black crime. Of course blacks hurt their own more than any other group. I think they're just violent by nature.
There are a lot of blacks that just don't like blacks though. I worked with one of them who, while she displayed some typical negro behavior traits herself, was very discriminatory against her own race in many ways. She would not hire black males, and she would have the entire crew of the store be on the lookout for blacks that came in to shop.