I don't think anyone can dispute that a dog jumping up, chasing, barking, growling, nipping, biting is unacceptable. The grey area is how close to you is deemed too close.
More often than not people I pass want to stroke my dog, this makes it difficult for her to know what she is meant to be doing, even though she goes to training most weeks. Do I say hello to these people or not?
I make a point of evaluating anybody coming towards us, any young children will have her brought to heel. Excited children and I will keep hold of her until they pass. Smiling cooing faces and I leave her be.
Dogs body language is so easy to read and I suppose I spend lot's of our walking time watching it. If she focuses on a jogger for example I whistle, she looks at me and fogets the jogger and gets back to sniffing.
As has been mentioned before it is deeply embarrassing if your dog misbehaves.