I think we've argued this before.

I carry bear spray, since that is the only reasonable option in my self-propelled adventures. Though there are other situations where I would consider a firearm.

From my point of view, a firearm carried for such a purpose should be capable of a clean kill. So, it should be appropriate in calibre and imparted energy, reasonably ensuring a rapid, humane end to the animal in question. I just don't see most pistol rounds being effective or humane in this context (though you use what you have, I guess). The hunting regulations in many areas spell out the minimum legal round for specific game, and to my mind that is a good place to start.

My 2c.

YMMV