Owned a restaurant once and never again. Had a whole family of 6 one time order huge meals, they all ate every bit then claimed the food sucked and wanted comped for the meal. Told them no they would pay for it because they ate it. The father gets pissed and threw his plate on the floor, beaking it, then threw his drink on the floor splashing others. I calmly told him the meal price just doubled with the added cost of the dishes, and he got more pissed. Started swearing and yelling. Told my server to go call the cops. Dude calmed down. I got his credit card and charged him double the meal price. The next day he tried to charge back the bill saying we defrauded him. Ended up I kept the money and sent him a no trespass letter, banning him from the restaurant...turns out his was banned from dozens of places. Once an asshole always and asshole who is teaching his kids to be just like him.
Thing about almost all people is this: If they were jerks growing up they just become bigger jerks when the get older. They never do grow up.
I have seen this same scam you describe pulled several times. It takes brass. What you did is spot on correct but never bluff.
It is easy to let one bad apple spoil the whole bunch but a lot of people are just no damn good. After being o for 3 on renters in a house I bought with a larger deal I tore the house down. Never again. Some say it was the class I rented to but I’ve seen the same or worse in high end rentals. I’d imagine the same goes for restaurants.