When you see someone walking a dog in a park or open space, and the dog is on a lead, it will be on that lead for a reason. They are probably either trying to stop it interacting with someone or something, or they are trying to reduce the likelihood of someone or something interacting with it. So if you see someone doing this, don’t allow your dog to run up to investigate it, as you may significantly increase the likelihood of something unpleasant happening. You could also force someone who is already sacrificing their dog’s freedom to keep you, yours and theirs safe, to have to work a great deal harder to do so. And if an incident occurs because you didn’t control your dog and keep it away from theirs, don’t then have a go at them because your dog gets attacked, or because they ask you in no uncertain terms to keep your dog away. They were trying to act in everybody’s best interests, including your dogs. Perhaps you should do the same. Shouting “It’s all right, he’s friendly”, or “He just wants to play” really doesn’t help. You don’t have the right to force everyone to have to interact with your dog because you can’t control it, and want it to be free. If you can’t control your dog when it is off the lead, keep it on a lead until you can.