First of all, I am a dog lover. But, if my dog is on a leash, and there is loose dog that is threatening, my job is to protect my dog. So in areas like this, I try to keep least 3 small rocks in my pocket. I watch the potentially aggressive dog's body language. If it starts to approach, I throw one of the rocks near the dog, to make it bounce several times near the dog, as a Warning. That usually works. If the dog still decides to approach, I throw the 2nd rock, aiming to hit its haunches. After that, all I usually need to do is raise my arm with the 3rd rock, threatening to throw it. The dog usually leaves at that point.

I did live in an area in southern Mississippi where several dogs would roam together free and try to attack my leashed dog together. It was very scary. So I ended up carrying a small hammer on all of my walks. And tgere was more than one occasion where those dogs were hit in the haunches with that hammer.