None of you are unreasonable in considering that dog owners should keep their dogs on leads in places where signs or bye-laws tell them to.
However, you are wasting your time trying to educate these inconsiderate animal owners.
Start a public campaign instead. Persuade your local politicians to have the law changed making it illegal for dog owners to let their dogs run loose, unless in a fenced area specifically designed as a dog-run.
Here in Denmark these rules are in place and dog owners are fined if they do not obey them. They are also liable for any damage their dogs cause, whether while on a lead or loose and must have an insurance policy that covers this.
Germany has even better laws - there you must attend dog-training classes run by the police with your dog in order to get a dog license and dogs are not allowed to run loose.
The minute you cross the Danish-German border which I do daily as I live practically on the border, you notice the difference.
German dogs walk sedately beside their owner, sit down when approached by other people, never jump up at you, and only bark on command - they even stop barking immediately upon being told "Sehr gut, sehr gut" - roughtly translatable as "all right now"
Try to get these rules made law in the UK - it make life much easier for everyone who is nervous around dogs, for the dogs' owners, and, as far as I can judge, for the dogs themselves.
Another thing, here you are not allowed to take a dog into any place where food is served, consumed or sold, basically no dogs in supermarkets, food shops, pharmacies, restaurants or cafés except guide dogs for the blind and helper dogs for those with mobility issues. Usually neither dogs nor any other pet will be allowed into a hotel. If you travel with your pets, you either make the journey in the course of a day, or if that is not feasible leave the animal overnight in the car.