I've been backpacking for about 20 yrs now. I've never seen a feral dog. I've seen some anti-social & aggressive dogs that their owners said, "Oh, he won't bite." I've seen a lot of snakes over the years. I hate snakes. But, they're usually easy to avoid if you watch where you put your feet & hands.
Pistols can be heavy & a pain in the butt to carry. Lots of issues to worry about: Where do I carry/hide it? Is it safe to leave it when I do a camp chore? Is it safe from the weather?
What people take on their backpack trips is based on their fears. Based on my fears, I wouldn't consider carrying a pistol on the AT. To date, I haven't felt it necessary to carry on any of my other hikes as well. If I ever do a trek in Afghanistan (or similar locale), that would change.