If he'd ever worked in a cafe or coffee shop that didn't have those rules, he'd want them plastered up on the wall.

First of all, you get the pissy customers who come in to take every one of life's problems out on someone who can't retaliate for fear of losing their job. Secondly, you get the customers who blatantly try to steal; they'll order ABC at $2.79 but when it's being made, they'll say they ordered DEF at $4.79 and that they're making the order wrong. The time to speak up isn't when you've paid and it's half-way made, it's when you visibly see them enter it wrong, however these people know it wasn't entered wrong.

From time to time, you'll occasionally get a variant of type 1, who'll come into the store and order their coffee wrong (ex. they want a black coffee, but they'll order 'coffee, no cream, no sugar', which means you'll get coffee one cream, one sugar, because a black coffee is a black coffee and isn't said any differently anywhere in the anglosphere, don't be different), they'll then proceed to swear at the staff in front of a line of customers. As a customer, I've had to tell these people to leave before and I've seen several others who've had to do it; it's flat out being a bad person and when these people have shirts and ties and company logo's plastered on their vehicles, they deserve to be fired because I'll never use their company. I expect more out of someone in a business suit, and I frequently see worse language and behaviour than anyone else.

I know for a fact that if I ran my own cafe/coffee shop, I'd have those exact rules. I wouldn't have them plastered on the wall, but they'd sure as hell be enforced on any jackasses who don't know how to behave in public. Life has rules and boundaries, and far too many people don't understand this. I was taught this in childhood, I assume everyone else was, but mature fully grown adults don't seem to grasp this.

I've seen this behaviour in convenience stores and supermarkets, in the lobbies of companies and in high-end restaurants, and all of their responses are: please leave the premises, and in the case of the swearing psycho's they've had the police called on them. I've heard even more stories about this going on. So why a small diner can't enforce the same rules is well beyond me. I've seen at dentist offices that they'll kick out the people chatting or texting away on their blackberries for no other reason than it's annoying to both staff and the others waiting.

There's an established etiquette in the world, just like there's an established etiquette on HN and anywhere. I don't go into a full-out swearing tirade against PG for some perceived wrong caused by myself, no one else does either. Why people believe they don't have to follow the rules is beyond me, and I believe these people should be punished to the full extent the law allows because the law is there to punish those that don't follow societally established rules and boundaries, AKA societal etiquette.

If I try to rip you off, I expect you to deny me service.
If I swear at you endlessly, I expect you to deny me service.
If I'm misusing your property, I expect you to deny me service.

I'm sorry, to me these are a given and don't need to be up on a wall. For way too many people, it's not a given.