President Trump’s pick to head up the military health system lunged into the U.S. gun debate Tuesday during a Senate hearing, saying laws allowing civilians to purchase long guns like the Texas church shooter are “insane.” Dean Winslow, a professor at Stanford University, offered up the assessment, seemingly unprompted, amid questions from Sen. Jeanne Shaheen, D-N.H., about the military’s treatment of domestic violence convictions during his nomination hearing to be assistant secretary of defense for health affairs. Shaheen asked specifically whether Winslow believed a person such as Devin Patrick Kelley, who was jailed by the military for assaulting his wife...