Back circa 99/00, I was head cashier when an ornery geezer went ballistic when one of my younger charges said “no problem” instead of “you’re welcome.” To keep from escalating things, I let him give his stupid lecture, but he wouldn’t stop and just leave. I finally interrupted and said it wasn’t worth getting so mad over and asked him to go.
After, I reassured my employee that we weren’t an Are You Being Served type of store. He was getting rung up for a paintbrush or something, not getting fitted for a tuxedo.