Okay, here's my take on the whole thing. I just hope I don't offend anyone.

I think your dog should've been on a leash. That's why there are leash laws. I dog sat one year for a friend in Vermont. He had a HUUUUUUUUUGE G.S. named "Striker" who was a great dog and very well behaved, except when it came to other dogs. One day I was walking Striker on leash, and another dog came out from his yard and tried to attack Striker. I panicked because I didn't want to get in the middle of it and the owner was nowhere to be found. Fortunately, I was able to get me and Striker away before it got REAL ugly.

So, IMHO, you were wrong to have your dog off leash in a public park while there were other dogs around. *sorry*