What are you actually disappointed about and what did you actually expect to happen? Did you want the dog put down for barking at you? Did you want social services to take the child because their mother allowed them to go outside their house?
You sound like you worry and overreact about everything and an absolute fun sponge!
Was it wrong that a dog escaped its house and barked at you? YES
Just because it barked and snapped does that mean it was trying to bite you? NO
One of my dogs will choose random people on walks to bark and snap at, he is never allowed off lead to ensure safety. However we have tested this with volunteers in controlled fields and given the chance he will run up, bark and snap and then the minute he gets attention roll over and turn into a softie, he has never once bitten anyone. But he does bark and snap so two different reactions not the same thing.
Should you have shouted at a 6 year old? NO
Should the mother have apologised for the dog? YES
Should you have apologised for making her child cry? YES
Overall should you be "rooted to the spot in fear" because a small dog is barking at you? Possibly if you have a phobia etc but as you are a dog owner yourself get over it and just keep walking, if it follows you barking so be it.
Was it a crap situation yes, was it one where everyone did something wrong yes, was it one you should have forgotten about and moved on from long ago yes.
On your latest post... how dare she come out in bare feet! Please someone consider the effects this will have long term.... What the hell does it matter what she wears, I will go barefoot as often as possible its so much more comfortable, regularly go outside to do the bins etc in bare feet.