I wanted to thank everyone for their responses. I really really want to ask people to please try to respectfully share their differences of opinion. I don't think criticizing other people's etiquette choices is productive. I am interested in hearing people's personal anecdotes, as all experiences and feelings are valid and help give us perspective.
It seems that my use of the word "parenting" has caused a little *ahem* disagreement among a few people. I wasn't really asking about "parenting" a stranger's child as much as how to deal with misbehaving children. I personally don't think basic rules of civilized society are only to be taught to children by their parents - though it is nice when parents make the effort. I would say it falls under the parents job description, but I don't think a stranger is overstepping their bounds by reminding a child when they interact with them.
Of course parenting is for parents - hence the name.
But I would suggest that while only parents (or guardians to be PC I guess) can parent (if you define parenting as discipline/control/ethically guide etc.), a child can learn
IMHO that is where the idea or perhaps the real spirit of "it takes a village" comes from - a child learns how to get along in the big outside world by going out in it and interacting with the other people they have to share it with.
Slightly new thought/direction on the issue: I have observed an interesting phenomenon with dogs - they have a "cut off point" for puppies that make breaches in dog 'etiquette'. Basically, young puppies get away with almost anything because they don't know any better and are given a certain amount of slack. Then the grown-ups decide that it's time for the puppy to grow up and learn manners and start biting their heads off (not literally but verbally!
) when they go over the line. So a puppy that had free reign over the food dish is suddenly chased away and basically told by the older dog that "I'm in charge so I'm eating first." Or a puppy that enjoyed jumping on his older friend's head is now pushed away for playing too rough.
Obviously we aren't dogs, but we are responsible for showing kids what is and is not acceptable behavior. The first thing that comes to my mind when a parent excuses their kid's behavior with "s/he doesn't know any better" is "well, why haven't you told them?"
In the grown-up world, "ignorance of the law is no excuse."
I'm sure this is a very individual/case-by-case thing, but how would others here usually decide that it is time to stop "humoring the puppy" and start trying to teach some etiquette?