The rule makes no sense. If they want a no barking rule make one. But don't make unenforceable rules.
Do they really check unoccupied RV's to see if there are pets inside? Or do they only respond if there is a complaint like most reasonable places.
If the dog is inside and doesn't bark what's the harm.
I do agree their park there rules. I hope they actually enforce the policy otherwise it just chases away business.
If they don't enforce it, but use the rule as a means to strictly enforce a barking policy than maybe it's OK.
In retrospect if they actually enforce and check unoccupied RV's for pets I would not want to stay there with or without my dog. Too much big brother for me. Fortunately there are other options.