Murders and shootings have spiked in many American cities—and so have efforts to ignore or deny the crime increase. The see-no-evil campaign eagerly embraced a report last month by the Brennan Center for Justice called “Crime in 2015: A Preliminary Analysis.” Many progressives and their media allies hailed the report as a refutation of what I and others have dubbed the “Ferguson effect”— cops backing off from proactive policing, demoralized by the ugly vitriol directed at them since a police shooting in Ferguson, Mo., last year. Americans are being asked to disbelieve both the Ferguson effect and its result: violent crime...