If you see a set of rules that don’t make sense, that are overly stern, that seemed designed to be offputting instead of helpful, it’s possible that the poster is leaving part of the memo unsaid:
It could be something like:
THE LAST CUSTOMER WAS UNFAIR AND UNKIND!
And so the list of rules to make sure that this never happens again, even if the next customer isn’t like that at all.
Or:
WE’RE STILL REELING FROM THE UNEXPECTED THING THAT IS PROBABLY NEVER GOING TO HAPPEN AGAIN, BUT ONE WAY TO DEAL WITH THE TRAUMA IS TO ERECT SIGNIFICANT BARRIERS SO WE’RE SURE IT WON’T HAPPEN AGAIN.
Or:
WE GOT INTO THIS BUSINESS BECAUSE WE THOUGHT WE LOVED BOOKS AND THE PEOPLE WHO BUY THEM, BUT THE REAL REASON IS THAT WE MISTAKENLY THOUGHT WE COULD MAKE A GOOD LIVING WITHOUT ANNOYING PEOPLE BOTHERING US! ESPECIALLY CUSTOMERS AND PEOPLE WHO CAN BRING US CUSTOMERS.
THIS IS MUCH HARDER THAN WE THOUGHT, AND WELL, MAYBE IF WE MAKE A LOT OF RULES, PEOPLE WILL LEAVE US ALONE.
You certainly don’t have to put the all caps part in when you publish your rules, but it might be helpful to write it out to be sure it’s what you really want to be implying.