The relationship between police and blacks is destructively fraught with grievance and blame. That's why the speech NYPD Commissioner Bill Bratton gave this week in a crowded church basement in Queens is so important.

He acknowledged the distrust seeded historically by the role of police in enforcing laws that were the foundation of slavery and Jim Crow discrimination. And he talked frankly about the risk that attitudes born of policing neighborhoods where most crimes are committed by blacks can unconsciously harden into bias against all blacks.

The goal, Bratton said, is to make the city "a place where working folks in neighborhoods afflicted by violence don't get treated any differently than working folks in neighborhoods where shots don't ring out."

Those are critical messages for officers to hear.

FBI Director James Comey cited the song, "Everyone's a Little Bit Racist," in making similar points in a recent speech at Georgetown University in Washington.

Police should be receptive to this message coming from their own. If heeded, it could mark a positive turn for the city and the nation after so much turmoil generated by the deaths of Eric Garner in Staten Island and Michael Brown in Ferguson, Missouri.

But understanding the friction between cops and blacks isn't enough. Critics of the police should stop condemning all for the actions of a few. NYPD officers use force of any kind in only two out of every 100 arrests, Bratton said, and crime has declined dramatically.

But the NYPD and other departments have to root out officers who do treat blacks differently from others they police. That should start with Officer Daniel Pantaleo, who, facing no threat to his life or safety, grabbed Garner in what so clearly appeared to be a banned chokehold, leading to his death.

It won't be easy to convince blacks that the NYPD takes claims of discrimination, disrespect and abuse seriously, or to persuade cops to examine and, where necessary, change their behavior.

But that's what it will take to heal.