I think if it is a unleashed dog beach everyone has a right to walk their dogs there off the leash...as long as the dog is well behaved and socialises well with other dogs. If you know (aimed at anyone...not specifically you) that your dog may attack other dogs or you do not have control of your dog then it is your responsibility to keep it on a leash.

I do not think you are in the wrong for walking your pups off their leash, sounds like her bigger dogs were the culprits and you cant blame a dog for defending itself. Hope your pups are ok