I go to an off leash park all the time and dogs are all over the place, off leash and having a ball, but these dogs are for the most part not aggressive and are under control. My comment does not mean I have the same attitude as these people you confronted, I just don't appreciate small yappers that carry on with lots of aggression and noise when they happen to meet my 'on leash dog' and I feel the small dog needs to be trained to be around other larger dogs or kept in a handbag where it's nice and safe. There is nothing more annoying than a little dog coming up to your dog and snapping and yapping with full snarl in action and carrying on like a pork chop, it makes me worried my dog might bite the little dog and then that makes me feel bad as I don't want to see any dog hurt, ever. And the owner of the small yapping dog will be equally very upset and I would not want that either.
The fact one of these people you met came back up the path to punch you hints that you were still yelling back at them? Not condoning the punching but seems this whole meet and great could have gone down a little better! Sorry to hear you had a bad day.