The left wants to blame these outcomes on racial animus and “the system,” but blacks have long been part of running that system. Black crime and incarceration rates spiked in the 1970s and ’80s in cities such as Cleveland, Detroit, Chicago and Philadelphia, under black mayors and black police chiefs. Some of the most violent cities in the U.S. today are run by blacks.

The jury’s only job in the Zimmerman trial was to determine whether the defendant broke the law when he shot and killed 17-year-old Trayvon Martin last year in a gated community near Orlando, Fla. In cases of self-defense, it doesn’t matter who initiated the confrontation; whether Mr. Zimmerman singled out Martin because he was a black youngster in a neighborhood where there had been a series of burglaries by black youngsters; or whether Mr. Zimmerman disregarded what the police dispatcher told him before he got out of his car. Nor does it matter that Martin was unarmed and minding his own business when Mr. Zimmerman approached.

All that really mattered in that courtroom is whether Mr. Zimmerman reasonably believed that his life was in danger when he pulled the trigger. Critics of the verdict might not like the statutes that allowed for this outcome, but the proper response would not have been for the jury to ignore them and convict.

Did the perception of black criminality play a role in Martin’s death? We may never know for certain, but we do know that those negative perceptions of young black men are rooted in hard data on who commits crimes. We also know that young black men will not change how they are perceived until they change how they behave.