From reading all of this, I get something a bit different from it. While I COMPLETELY agree that they should have let those folks stay for dinner without any of the fuss and muss, and that the subsequent events were outrageously inappropriate, I don't think the motivation for kicking them out was because they wanted to stay for dinner.
From a complete impartial observer, the anger came from the "borrowed" tag. Now the staff is just sure that there is a bunch of other "thievery" going on. Rather than solve the problem, they let anger rule the day. Not a good practice.
It seems to me that the appropriate solution to this, with much less involvement of staff and emotions, would have been to allow the car to visit the other campers. Then, a couple of hours later, one staff could have driven by and reminded them to please be on their way or pay for camping.
I'm not a camper so I won't be going there. But if I were a camper, I still wouldn't go there. With the amount of distrust by the owner/staff, it seems likely that they exhibit some of the behaviour that warrants mistrust. That is frequently the case.