Being a pet owner, I view this in different ways. First of all, I don't mind a pet fee, but the park needs to be priced otherwise to meet the amenities. Just like when the State of Virginia was charging $5/pet and their fees for a start park already was higher than other states. Plus you could get a site elsewhere at a private opark with more amenities for the same price or less.
On the other hand, I don't care too much for those who bring numerous dogs and set up fences and etc outside. It would be different if they didn't yap all day long or everytime they see another dog or a person walks by. But thats just my opinion.