"Signaling to shooting victims, their families and the American people that heinous acts like those in Gilroy, Calif., and El Paso, Texas, and Dayton, Ohio, are unacceptable is the right thing to do. Americans know bad people will sometimes do bad things, no matter how hard we try to stop them, but we expect our politicians to counter such horrors with their best efforts," says columnist Scott Jennings. Trump has an opportunity to do that, and simultaneously splash mud on liberals who politicize these tragedies. Here’s how."