THIS TIME it was George Floyd; history suggests there will be a next time and a time after that. African Americans are so regularly the victims of unjustified, unprovoked, unforgivable police violence that it would be willful blindness to think that a pattern so entrenched will suddenly cease.

Protests and rage have erupted in nearly a dozen U.S. cities not only because a white police officer coldbloodedly cut off Mr. Floyd’s air supply, kneeling on his neck until life seeped from him, but also because that was just one of many such frequent dehumanizing episodes. His death is a reminder of the quotidian assumption forced on so many African Americans — that their lives are cheap, and may be extinguished at any time and anywhere by a man in a uniform with a gun.

President Trump has seized on the cascading violence in Minneapolis to do what he does best: inflame, divide and, most of all, distract — even as so many Americans reel from the ravages of disease and unemployment. Like Richard M. Nixon, George Wallace and other race-baiters before him, Mr. Trump regards the country’s schisms as an opening — an opportunity to embrace law and order, threaten military action and galvanize his white, working-class base. It’s a despicable strategy; it diminishes America; it also has worked for him until now.

The president hails the heavily armed white protesters in Michigan, who menaced public officials to oppose the pandemic lockdown, as “very good people”; he denounces the mostly unarmed, racially diverse protesters in Minneapolis as “THUGS.” It is left to others to put the fury and fires that have followed Mr. Floyd’s death in context. “The ashes are symbolic of decades and generations of pain, of anguish,” said Minnesota Gov. Tim Walz, a Democrat.

Some U.S. police departments, and many officers, have taken history’s lessons as a rallying cry for reform. A New York City detective, Dmaine Freeland, posted a video this week to denounce Derek Chauvin, the Minneapolis officer who bore down on Mr. Floyd’s neck. Mr. Chauvin, said the detective, who is African American, “is not my enemy because of any race, creed or color, but he is my enemy because he brought dishonor to the uniform and the badge.”

By contrast, Minneapolis’s own police have done little to suggest they can earn the trust of the community they are sworn to serve. They have not released body-cam footage of Mr. Floyd’s arrest, nor apologized for the specious statement they published about the incident, which elided the fact that Mr. Chauvin’s knee choked Mr. Floyd. The head of the city’s police union, Lt. Bob Kroll, said “now is not the time to rush to judgment” on Mr. Chauvin or the other officers at the scene, who did nothing to interfere as Mr. Floyd begged for his life.

On Friday, Mr. Chauvin was arrested and charged with murder and manslaughter. An FBI civil rights investigation of the incident is underway; the Justice Department says it is a top priority. Much more will be required to quell the fury in Minneapolis and across America, confronted once again by bigotry and police brutality, which to too many Americans comes as no surprise at all.

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