black on black crime was used to deflect from conversations on institutional racism — thewonder
Talking about X doesn't automatically mean you are deflecting Y, rendering Y invisible, denying Y, and so on. X and Y are separate topics. Black on black crime is local, it bleeds and leads, and is very concrete. Institutional racism, sexism, or some other 'ism' is general, usually blood-free, and is abstract. it usually is a political construct (whether it is real or not).
Topic deflection certainly occurs. If I am talking to you about how "banking has historically discriminated against blacks", and you respond by saying, "Yeah, but blacks kill each other at much higher rates than whites kill each other"--that is deflection. if you hold a conference on the history of banking discrimination in black communities, that is not deflecting the question of black on black violence. You are simply talking about something else.
Back in the 70s, if a heterosexual feminist gave a speech about the problems of women in the workplace, one could count on a lesbian activist standing up and accusing the speaker of "rendering lesbians invisible". Lesbians faced workplace problems that were different than, and the same as, those faced by heterosexual women. Then a minority woman would accuse the white woman of rendering minority women invisible. The lesbians and minorities could agree that heterosexual white men were oppressing them, as long as they didn't have to acknowledge each others' suffering. Sometimes race would trump sex, and white women would be grouped with white men as a common enemy.
No matter your political stance, sex, sexual orientation, age, race, ethnicity, class (working, middle, ruling), or your personal history -- someone will always accuse a speaker of devaluing, rendering invisible, ignoring, deflecting, denigrating, and so on. (We could get into how the aristocracy of suffering works, but that's another can of worms.)