I would do what you did..get mad at the owner for not taking her dog off of my dog, now that might not be the correct way to do it..but I am very emotional when it comes to my family and lets face it, my dogs are part of my family..
If Otis gets in a snarkfest at the park, I will let them sort it out..but if he is no longer part of the festivities, whether he has come back to me, or walked away to a different area of the park..I would get my dog out of that area or park immedietly, no one wins in trying to prove a point..even if you are in the right..it isn't worth your dog getting hurt because somebody else wasn't doing what they ought to do..boy that is hard to follow through on though..my emotions run high when this type of thing happens.
Otis is very much momma's boy at the park, he will go away to check things out, but comes back periodically to check in..if snarks erupt he will be the first to come running back.
Once we went to the park and this one lab/dachshund mix just beelined to Otis and attached himself to Otis' neck..they sorted it out and off we went..a few minutes later this dog does it again, this time Otis came running back to me, with the dog attached to his now very straight tail..and the mutt kept on doing that through our whole stay at the park..he just had it in for Otis, and poor Otis had no clue why.
The owner just said that he will do that, just ignore him..IGNORE him, are you kidding me..no way..you take your mutt dog out of here if he is causing trouble time and time again..once they left some other people came up to me and said they were happy I had said something to him, because that dog always causes problems.
I hope all this made sense..good luck at the park, but remember, nobody will look out for your dog but you..if you sense trouble, just leave..it isn't worth Gizmo getting hurt.