Police Commissioner Bill Bratton now says he was misunderstood when he cited the late Sen. Pat Moynihan’s 1965 report on the deterioration of the black family while discussing a national rise in homicides.

The landmark report is controversial because critics wrongly called it racist — though even President Obama has defended the study and praised its warnings.

Mayor de Blasio took issue with his commissioner, calling the Moynihan report “outdated” and “irrelevant.” No, it’s more relevant than ever — because the problem’s spread.

Moynihan sounded the alarm when one in four African-American births was out of wedlock. Illegitimacy is even higher than that in white America today. The Center of the American Experiment calls “family fragmentation” — high rates of illegitimacy, divorce and single-parent households — “the biggest domestic problem facing this country.”

On the other hand, the decay has been going on since before 1965 — so the challenges it poses, to policing and to society as a whole, aren’t new. It certainly can’t explain a rising tide of urban homicides. After all, the same forces were in play when better policing drove crime to historically low levels.

Moynihan warned that the collapse of black family life would mean rising crime and chaos affecting African-Americans as victims. Now a broader family collapse poses the same threat to other communities.

But that’s a long-term social problem policing won’t solve. The cops’ job is to fight crime. And that’s what Commissioner Bratton should be talking about.