There are two golden rules for gun safety. Rule one, never point a gun at something you don’t want to destroy. Rule two: keep your finger off the trigger until you’ve decided to destroy it. “Muzzle discipline” means more than avoiding placing hapless humans in your sights. You should also refrain from potentially destroying your non-gun hand, your right foot, your neighbor’s extremities, the plexiglass range lane divider and anything else that might cause “issues.” To that end, follow the rabbi’s advice. Imagine there’s a five-foot flame coming out of the gun’s muzzle. By the same token, “trigger control” means...