These are not “assault rifles”, they are “mission rifles”.
An AR-15 rifle has a mission - to shoot that bear charging at you full tilt. Also to bring down that trophy deer. Or wild boar (which may also be charging at you).
“Gun free zones” are just shooting galleries, and the presence or absence of an AR-15 makes little difference if other sidearms are present. For those who have bad intentions, gun-free zones turn schools and other locations into shooting galleries.
I suppose you can shoot the bear with it. It’d be better than nothing most likely, especially since the noise or the sting might also deter the bear, but it’s not really powerful enough to be expected to drop a bear.
I don't ever really expect to use it to defend my family and home from intruders. I don't expect a zombie apocalypse. I don't plan on taking up arms against a foreign or domestic power. I don't "need" it to go hunting (and it probably wouldn't be my first choice for that task either).
I do expect it to help ward off would-be tyrants and fascists. By being one of the millions of privately owned firearms it represents a very real threat. It is the literal teeth in the 2nd Amendment. All you lurkers out there that support "gun control" by the government - you, yes you, are exactly why the 2nd Amendment was written. You are the primary reason so many of us have so many firearms. Your ill-considered zeal for control and regulation is what drives so many firearms sales. These firearms are a very real reminder that you cannot and will not simply take away our freedoms, liberties, and rights.
No offense, but those are not the AR-15’s ‘mission.’
The .223 cartridge is a bit on the anemic side for bears. They might be okay for deer.
But the .223 was designed for wounding men. It is also a pretty good target round.