I mostly love dogs more than people. I've been around them for more than 70 years and believe that I understand them pretty well. They, like us, are of all-sorts and normally respond to alpha behavior on my part. But, sometimes they need a more immediate instruction.
There is nothing better than pepper spray. I always have a can of foam-type spray at hand when I ride, or walk for that matter. Either in my pocket (walking) or sticking out of the top tube bag just behind the headset on my bike. The foam spray squirts a directional stream that does not splatter; it also pentrates wind. It does no permanent damage yet can stop a charging Grizzly in its tracks.
Water works, when the dog is not really violent. Vinegar or ammonia in water (three parts water) is better. Vinegar does no permanent damage; I am not sure about ammonia.
I've had violent dogs attempt to attack me: I kicked one, got him really good, and he would thereafter run to and stay on his porch when I rode by. I gave the other two a snootful of pepper spray. One of them was an extremely aggressive pit bull with an equally violent owner who then also attacked -- got the same treatment and a visit by the sheriff. I never went by that house again and learned a few months later that the man had shot himself to death. Poor dog. I also learned that the other dog I sprayed never chased another bicycle LOL
Pepper spray works and does no long-term harm. My county's sheriff's department (and most police I suspect) prefers that you use pepper spray over a gun (Duh); when I called them about the guy and his pit bull and told the deputy what I had done, he said, "Right On!"
On the other hand: A dog who chases while wagging his tail is playing. But, look out for bared fangs (the lips are pulled back), stiff tail and raised hackles (the back hair behind the neck) -- you can shoot that one for all I care, that is a ruined dog and children may be at risk.
In the summer '59 I had to shoot a dog, the only time I've ever personally killed one. I was 17 years old and hunting rabbits (yes we ate them) in the desert near Alamogordo NM when I ran upon a pack of feral dogs. They were clearly a family and I think they might have been Labrador Retrievers. There were nine of them, three were maybe six months old. They were running like coyotes do when hunting. They turned toward me and started to run faster. Their intentions seemed clear to me and it was not to play. I fired into the sand in front of them twice -- didn't change a thing. So, I picked the Alpha and shot him. It was a head shot and he dropped like a stone. The others stopped, milled around a bit and, when I fired into the sand close to them a couple more times, they took off -- as did I!
Told the warden and sheriff's office. They baited and killed the rest of the pack. Kinda wished I hadn't said anything, but -- it coulda' been a kid.
And, well, damn the ignorant, stupid or twisted people who don't take responsibility for their animals. I've never seen a 'bad' dog that wasn't made that way by one of these creatures.
Joe