When I was growing up on a series of Marine Corps bases across the country, the phrase “man with a gun” was comforting, not scary. Yet as the anti-gun movement gradually took control of the public debate, it became not just frightening — especially to those who knew nothing about firearms — but a matter for instant police action. Today, with open-carry laws proliferating — Texas is about to adopt open carry — the sight of a civilian packing heat may be the New Normal. But what are the etiquette rules so we don’t frighten children, horses and the Pansy...