A dog attacking another dog that wanders into its fenced in backyard is very different that a dog attacking a child that wanders into a campsite.
My point is that if the large dog's owner is following all the rules, the dog is under control, and they are on property legally, then when a small dog's owner is NOT following the rules, the small dog is NOT under control, and/or they are NOT on property legally, then we shouldn't blame the dog for reacting in a manner consistent with dogs.
I've had many more small dogs run over to my dogs in an aggressive and threatening manner than I've had large dogs do so. If the small dog is initiating the aggression, then the small dog owner needs to take on at least partial responsibility for the ensuing events.