While walking dogs in the evening, I often encountered joggers who run up on us, sometimes from behind, acting as if they own the sidewalk. My dogs are city dogs, have been exposed to this from puppy hood and pay little attention. One time a jogger came up from behind, actually brushed against me on a narrow sidewalk and almost knocked me down. Fortunately Sidney did not react with aggression, but in that case it might have been justified. I was extremely angry and yelled at the jogger who just laughed. I was angry not because I was injured, but because of what could have happened. My hands were shaking as I gave Sid a hug and told him he was a very VERY good dog. I was angry at the jogger for being so stupid, and for setting himself up for a dog bite injury. Had Sidney thought he was protecting me from that idiot, he would have been labeled a "dangerous dog" - for attempting to protect me in a situation he preceived as threatening.
My dogs are all trained, well socialized, and respond in a friendly fashion when properly introduced to strangers. HOWEVER, I have no doubt that they would protect me if needed. Most dogs will protect their owners, and Dalmatians as a breed are no different. I would expect them to protect their owners. They don't understand the concept of "jogging". A stranger running up on us in the dark, from behind, saying nothing, could easily be perceived as a threat, particularly to a reactive or under socialized dog. I cringe as I watch joggers running up on dog walkers, never even considering the possibility that a dog might see them as a threat.
Not all dogs who are out walking with their owners are well socialized, properly trained companions. Some are rescue dogs from questionable backgrounds, some are poorly trained, out of control pets, or under-trained reactive adolescents, while others are simply from protective breeds, often with clueless owners. One of these mornings I expect to wake up to a news report of some "unfortunate" jogger who was bitten by a dog while out running, and I will wonder who was actually at fault. An unthinking jogger, a dog walker who did not have control of his dog, or a dog who simply perceived a threat and acted accordingly.