In the wake of the recent mass shooting in Colorado, New York Mayor Michael Bloomberg called on police to join him in fighting for more gun control: "I don't understand why the police officers across this country don't stand up collectively and say we're going to go on strike." It is illegal for police to go on strike, and Mr. Bloomberg later backed off his statement. But the mayor is just as far off the mark in his assumption that police agree with him on gun control.

Take the annual survey by the National Association of...