I don't go to dog parks, either.
In general, I don't think it's a good idea to let your dog handle the situation.
Of course I'm going against my own actions -- Years ago, I had little yapping foo foos always coming after my dogs, biting at their ankles, when we'd go on our daily walks at a big park. After months of being "attacked," and the idiot owner doing nothing about it -- not even calling his dogs -- I allowed my Morgan to take care of the situation:
Main Foo Foo came up, as usual, snapping and growling at Morgan's ankles. Morgan, in one swift move with just the right amount of force, reached back and snapped at Foo Foo, nailing him just a little. I heard a little "yelp!" and Foo Foo ran. Never again. It never happened again. I walked away with an evil grin.