A lot of people don't understand dog behavior or just don't care. They can't imagine their cute and precious dog being a problem or just don't care when it is. That's partly why dog parks can be so hit or miss.
I would warn you to be careful playing fetch there especially if you're using a chuck it as that's generally longer range. Toy aggression can cause fights to break out and if you've already had incidents so close together there's definitely the potential there. Some dog parks ban toys, I wish all would and enforce it. I know they're good places to go and run off steam but if you haven't thought about it before it's something to think about. If you're alone most of the time then probably not an issue.
I could see that being a problem, but frankly we wouldn't go if it weren't for fetch. Normally I keep Jupiter running most of the time so he doesn't get into trouble.
Today there was this weird dog who had his ball in his mouth the whole time and kept chasing Jupiter around and kind of ramming him in the ribs until Jupiter started to fight back and bite him. The owner didn't seem to notice his dog kept pestering my dog, chasing him all around the park, repetitively, or that Jupiter was starting to get annoyed.
Most of the owners and dogs at this park are good, but then you get things like this and makes you wonder. I know there are incidents, sometimes serious ones, and I guess we all have to weigh things in our own way.