Pinning other dogs to the ground at the dog park isn't okay. I had a dog who would do it and he would just basically give sweet innocent dogs a mean look and they would flop over and he would stand over them, probably not even touching them. But that is very aggressive and inappropriate behavior. It really fucks up other dogs. With my dog aggressive dog the best solution was to not take him to places there would be off leash dogs- the dog park is the number one off leash dog place.

I've been to the dog park with friends and never had a random dog attacked me- is that really a concern? And should you really expect your dog to protect you? Why not protect him by not putting yourself in that situation?