The warnings began even before Bill de Blasio was sworn in as New York City’s mayor in January 2014. A safe New York depended on the aggressive policing tactics that began in the 1990s and flourished under Mayor Michael Bloomberg and his police commissioner, Ray Kelly. Without those tactics, the doomsayers said, the city would be swamped by a 1970s-style crime wave.

After a federal judge ruled in 2013 that the Police Department’s “stop and frisk” policy was so sweeping that it violated the Constitution, Mr. Kelly was furious. “Violent crime will go up,” he said on NBC’s “Meet the Press.” “No question about it.”

That prediction has, of course, been proved wrong, ...

Read the full editorial here.