Its intersection with overly aggressive law enforcement was not random or inevitable, but rooted in a historical irony. As the political scientist Michael Javen Fortner documents in his forthcoming work “Black Silent Majority,” when Gov. Nelson A. Rockefeller of New York introduced draconian new drug laws in the early 1970s to combat the increasingly violent street life of New York City, he did so with the full support of black leaders, who felt they had no choice — their lives and communities were being destroyed by the minority street gangs and drug addicts.

But it was not long before the dark side of this intervention emerged: Soon all black youth, not just the delinquent minority, were being profiled as criminals, all ghetto residents were being viewed and treated with disrespect and, increasingly, police tactics relied on the use of violence as a first resort.

And yet it didn’t work, at least in one important respect: Although the black homicide rate has declined substantially, it still remains catastrophic, with blacks being murdered at eight times the national rate — and, among teens, it has been rising again since 2002.

In tackling the present crisis, it is thus a clear mistake to focus only on police brutality, and it is fatuous to attribute it all to white racism. Black policemen were involved in both the South Carolina and Baltimore killings. Coming from the inner-city majority terrorized by the thug culture minority, they are, sadly, as likely to be brutal in their policing as white officers.

We see this in stark detail in the chronic violence of New York’s Rikers Island correction officers, the leadership and majority of whom are black. We see it also in the maternal rage of Toya Graham, the Baltimore single mom whose abusive reprimand of her son, a video of which quickly went viral, reflects both her fear of losing him to the street and her desperate, though counterproductive, mode of rearing her fatherless son.

WHAT is to be done? On the police side of the crisis, there should be immediate implementation of the sensible recommendations of President Obama’s Task Force on 21st Century Policing, including more community policing; making the use of violence a last resort; greater transparency and independent investigation of all police killings; an end to racial profiling; the use of body cameras; reduced use of the police in school disputes; and fundamental changes in officer training aimed at greater knowledge of, and respect for, inner-city neighborhoods.