So much for the good guy with a gun. That, you will recall, was NRA CEO Wayne LaPierre’s preferred solution to America’s epidemic of firearms violence. “The only thing that stops a bad guy with a gun,” he said, “is a good guy with a gun.” He said this on Dec. 21, 2012 — one week after the massacre at Sandy Hook Elementary School that left dead six adults and 20 children ages 6 and 7. Americans were grieving and demanding action, and this was his answer. The “good guy with a gun” would set things right. To no one’s...