Joe Biden released a video the same day in which he asserted that all African-Americans fear for their safety from “bad police” and black children must be instructed to tolerate police abuse just so they can “make it home.” That echoed a claim Mr. Obama made after the ambush murder of five Dallas officers in July 2016. During their memorial service, the president said African-American parents were right to fear that their children may be killed by police officers whenever they go outside.

Minnesota Gov. Tim Walz denounced the “stain . . . of fundamental, institutional racism” on law enforcement during a Friday press conference. He claimed blacks were right to dismiss promises of police reform as empty verbiage.

This charge of systemic police bias was wrong during the Obama years and remains so today. However sickening the video of Floyd’s arrest, it isn’t representative of the 375 million annual contacts that police officers have with civilians. A solid body of evidence finds no structural bias in the criminal-justice system with regard to arrests, prosecution or sentencing. Crime and suspect behavior, not race, determine most police actions.

In 2019 police officers fatally shot 1,004 people, most of whom were armed or otherwise dangerous. African-Americans were about a quarter of those killed by cops last year (235), a ratio that has remained stable since 2015. That share of black victims is less than what the black crime rate would predict, since police shootings are a function of how often officers encounter armed and violent suspects. In 2018, the latest year for which such data have been published, African-Americans made up 53% of known homicide offenders in the U.S. and commit about 60% of robberies, though they are 13% of the population.

The police fatally shot nine unarmed blacks and 19 unarmed whites in 2019, according to a Washington Post database, down from 38 and 32, respectively, in 2015. The Post defines “unarmed” broadly to include such cases as a suspect in Newark, N.J., who had a loaded handgun in his car during a police chase. In 2018 there were 7,407 black homicide victims. Assuming a comparable number of victims last year, those nine unarmed black victims of police shootings represent 0.1% of all African-Americans killed in 2019. By contrast, a police officer is 18½ times more likely to be killed by a black male than an unarmed black male is to be killed by a police officer.

On Memorial Day weekend in Chicago alone, 10 African-Americans were killed in drive-by shootings. Such routine violence has continued—a 72-year-old Chicago man shot in the face on May 29 by a gunman who fired about a dozen shots into a residence; two 19-year-old women on the South Side shot to death as they sat in a parked car a few hours earlier; a 16-year-old boy fatally stabbed with his own knife that same day. This past weekend, 80 Chicagoans were shot in drive-by shootings, 21 fatally, the victims overwhelmingly black. Police shootings are not the reason that blacks die of homicide at eight times the rate of whites and Hispanics combined; criminal violence is.

The latest in a series of studies undercutting the claim of systemic police bias was published in August 2019 in the Proceedings of the National Academy of Sciences. The researchers found that the more frequently officers encounter violent suspects from any given racial group, the greater the chance that a member of that group will be fatally shot by a police officer. There is “no significant evidence of antiblack disparity in the likelihood of being fatally shot by police,” they concluded.

A 2015 Justice Department analysis of the Philadelphia Police Department found that white police officers were less likely than black or Hispanic officers to shoot unarmed black suspects. Research by Harvard economist Roland G. Fryer Jr. also found no evidence of racial discrimination in shootings. Any evidence to the contrary fails to take into account crime rates and civilian behavior before and during interactions with police.

The false narrative of systemic police bias resulted in targeted killings of officers during the Obama presidency. The pattern may be repeating itself. Officers are being assaulted and shot at while they try to arrest gun suspects or respond to the growing riots. Police precincts and courthouses have been destroyed with impunity, which will encourage more civilization-destroying violence. If the Ferguson effect of officers backing off law enforcement in minority neighborhoods is reborn as the Minneapolis effect, the thousands of law-abiding African-Americans who depend on the police for basic safety will once again be the victims.

The Minneapolis officers who arrested George Floyd must be held accountable for their excessive use of force and callous indifference to his distress. Police training needs to double down on de-escalation tactics. But Floyd’s death should not undermine the legitimacy of American law enforcement, without which we will continue on a path toward chaos.

Ms. Mac Donald is a fellow at the Manhattan Institute and the author of “The War on Cops,” (Encounter Books, 2016).