I would have lost it, if anyone threatened my dogs. Sorry. They cannot defend themselves, from idiots or their behaviour, without being labeled dangerous dogs, that is my job. You were definitely not wrong. HE was.
As far as the whimper, it may just have been that the smaller dog felt intimidated by a larger dog and wasn't even hurt a little bit, just scared and whimpered due to that.
I don't take my dogs to the dog park anymore, just because of situations like this. Max was running and playing with some dogs, the last time I took him. 2 lab mix dogs ganged up on him. Their fur was up, teeth snowing, growling and snarling, one on each side of him. He was dancing and jumping around, play bowing like crazy, because he is used to this, from our other dogs and wanted to play. The owner had a fit. Max was intimidating his dogs. Are you kidding me or are you just a moron?
I had Cody on a leash the same day, and had a little dog following us around mounting him. He growled at the dog, when it wouldn't stop and I grabbed the other dog by the collar and pulled him away from Cody, saying no loudly, to make him stop. I had moved Cody away from him, numerous times. The owner came up and was upset that I had "manhandled" her dog. I explained that if she was monitoring her dog's actions, instead of socializing and ignoring him, I would not have had to intervene. Her take was that if I was keeping Cody on a leash, he must be vicious and shouldn't be there. I explained that he would not be on a leash if everyone could control their dogs and not let them bully other dogs and attack other dogs. He feels like he needs to protect the underdog and I am not willing to let him do that.
Unfortunately, a lot of dogs are so entrenched as being the only dog and alpha to their people, they do not understand how to submit to anyone or to other dogs. They do not have any social skills whatsoever. They feel intimidated by larger dogs and have to put on their little doggy macho act. It is really humerous, but can be dangerous for them.
I really dislike stupid dog owners. They have no clue and do not understand that all dogs need to learn how to interact with other dogs and be corrected when they don't have dog manners. It is a shame that a few can spoil it for the majority.
Kathy