Tallying up kids killed with guns was not how I’d planned to spend my morning. Yet there I was, reading through a Mayors Against Illegal Guns report on mass shootings, counting the number of kids killed in domestic-violence related shootings between January 2009 and January 2013. Part-way through, I had to get up from the computer and give myself a break from the overwhelming sadness of my task. The families and friends of those children, though, can never walk away from the tragedy that happened to their loved ones. It is a tragedy that we, as Americans, have allowed to happen through our...