I still hold, that if your dog is on a lead, and another comes up to it and harrasses it, you have a lead in your hand, you have some control. The off lead dog owner clearly has none if the dog has refused a recall.
I would invest energy in training my dog, not other owners.
Being able to break a dog fight up is essential, for the very reasons given, that people do just let their dogs run off lead, regardless of what jurisdiction there is.
And a dog on the leash, is controllable. VERY.
If you are unable to control your dog, on a leash, then repeat your training till you have the control required to not be risk to others.