Parents? Would you EVER allow your kids to do this?

I think you are right the parents were being irresponsible as a parent myself if I ever see a dog I always tell my kids not to go near it I explain the dog doesn't know you and it might get a fright if you run over and start patting it and could bite you thankfully my kids understand this and don't go running to any dogs they see. If the owner gives permission for my kids to go near it then if they want to pat it fine but I would never think of just letting my kids run up to an animal and start touching it at the end of the day even the nicest dog can turn and if it is made to feel scared or uncomfortable then it is even more likely to do so. The sad thing that is and god forbid it happened but if the dog turned and bit a kid even after you saying not to let the kid near the dog the dog is the one who would have be put down! I don't blame you being angry I would be too. Unfortunately there is not much you can do about it all I'm afraid.