A couple of days ago, a white college baseball star from Australia, Christopher Lane, was running for exercise along a rural road in Oklahoma, my wife’s home state. He was attending college there. As he passed by three black teenagers, they decided it would be fun to kill him. They drove up behind him, shot him three times and he was dead. They apparently laughed about it and one of them posted an online comment about their exploit — shooting an unarmed man in the back and killing him — and how cool that was. They were quickly arrested and...