On my recent "Duval Delta" trip, I think I saw more dogs than I'd ever seen before.
95% of them weren't a problem. It may help that I'm going slower than a lot of you are, and it's kind of frustrating for a dog to chase something going slower than he is. It might help that I had on shorts and tee shirt rather than a superhero outfit. Anyway, I did tell them "Go back home" or words to that effect. I was hoping that the human voice would reinforce the idea that I wasn't some sort of alien invader.
Most of the dogs I saw, including the two meanest-looking ones, seemed to be defending their territory. Since I was headed out of it, they seemed to be hastening me on my way, rather than trying to attack me, and never got closer than 8-10 feet away.
The ones that really seemed closest to being a problem were a couple of strays. I think there were three dogs together, and when I passed, one started chasing me. Then a second one got encouraged by him, and took it up as well. But they chased me for maybe a half-mile or so. Veering towards them would back them off temporarily. I finally figured they must be getting tired, so I sped up to 22 mph or so and outran them.
Here's one I had to deal with recently back home. First time I went by, I wasn't ready for him. Second time, I had the camera out, but missed. Third time, I got him.
Back this fall, I was a volunteer at the Texas Time Trials, and I/we spent several hours dog-sitting at a house with loose dog(s). The main dog I dealt with was a medium size heavy-built dog. After we'd been there a little bit, he was pretty friendly. He was a country dog, was bored out of his skull, and had these odd looking people riding by in the middle of the night on bicycles with lights. I guess it's sort of like if UFO's started coming down my street, I'd be out there at the curb hollering, too.