This guy was not hunting. Hunting puts weird restrictions on firearms and ammo, but you don't have to follow them for self defense. It's only a moose that I'm talking about for 10mm, good quality 9mm defensive ammunition is good against pretty much everything else in North America, except some large bears.
Also as a hunter, I can envision a scenario or 4 where an animal might surprise me
Hog hunting springs to mind, that's the only sport hunting where I'd carry a .45 sidearm in addition to my primary rifle