I got to jump in here and put some myths to rest.
First off, I am big proponent of bear spray when moving through bear country, but here is a little news for some people....bear spray doesn't always work.
I've given full blasts (to an angry and confident black bear) and he barely flinched....and continued to march right into my camp and steal my food bag. That, and depending on the wind, that stuff can sometimes affect you just as much as it affects the bear, which is not a situation you want to be in.
Secondly, a firearm, even a 9mm pistol, is very much a good backup measure to have for bears (especially if we are talking about dealing with the bears in an escalating manner of 'verbal, posture, spray, kill/disable'). Everyone likes to tell old wives tales about that big/mean grizzly who took 5-6 shots of some small caliber and continued on his rampage....has that ever happened? Maybe, though I haven't seen or heard of it personally.
The reality is, if an animal, even a bear, gets hit by any sort of firearm projectile, he/she is going to seriously reconsider whether or not he wants to continue on his aggression or food-seeking. And if that shot is even somewhat well-placed (hips, chest, head) he/she is going to quickly lose the ability to function and move. More relevant, if bear hears the gunshot and the following crack of the bullet as it passes by him, he will be spooked or at least confused.
I hear a similar argument all the time within the firearm community: some people say that anything smaller than a .45 is not worthy carrying for everyday self-defense because the smaller calibers don't have enough "stopping power." Stopping power isn't a real term when it comes to firearm ballistics. A 9mm or even smaller will be sufficient for 99% of the self-defense situations you might find yourself in....that 1% (some aggressor with no mental inhibitions or high on drugs) might make it past the first 1-2 9mm shots, but you really have to be something special to ignore the next 5-6 shots.
The same applies to bears. Somewhere in the deep woods, is there a huge, BAMF of a grizzly that could soak up a shot or two from a small caliber pistol and continue his charge? Maybe. What's the probability of you meeting that guy? More importantly, what's the probability of that BAMF grizzly continuing his charge after he takes 4-5 more shots? The answer: very low.
Carrying a regular caliber firearm is very handy for bear defense. Obviously a shotgun or large caliber pistol would be even better, but how many people pack those kinds of firearms for vehicle or foot travel? The firearm's discharge, in most cases, will be more than enough to scare aware any would-be animal aggressors thus allowing the whole situation to be resolved without any loss of life.
If people want to hike/travel through bear country without a firearm, that's perfectly okay too as long as they take the right precautions (spray, travel in group, food bag up in the trees, ect.). But there is nothing wrong with traveling with a firearm; like everything else in life, it needs to be used responsibly and it certainly gives you more options when a situation turns bad.