There are basically two types of people who talk about Black on Black crime; racists who want to use the statistics to portray African-Americans as uncivilized and to justify bigoted policies; and people who are appalled that any segment of the population has to live in such violent conditions, and they want to work on improving the situation.
There is only one type of person, though, who does not talk about Black on Black crime: people who are fine with it. Which is to say, they are basically just a segment of the first group.