The dog park I go to does NOT allow aggressive dogs. Period. One of the "regulars" that I talk to often, has a little Westie who was brutally attacked by 5 dogs. The poor thing survived, but the owner of the 5 dogs was an @$$hole about it.

I would never stop going there, just because of a few irresponsible people. My dogs love it way too much, and I enjoy going. Mine haven't really been "bothered" by any other dogs, but if they were Molly would quickly end it. She stays very close to Daisy, and since Daisy is submissive when another dog comes up to her, she rolls on her back and Molly comes over and makes sure she's okay.

Our dog park also provides pooper scoopers for picking up after your dog, and a bunch of water bowls. They also require your dog to be current on all shots, be at least 4 months of age, but they don't require them to be spayed/neutered. (which I hate. )

Anyway, as to your question, if you thought it was aggressive, call it off. If it seems more like playing, let them be.