To address the argument "how is the hiker supposed to know if the charge is a bluff or for real?" This begs the question should there be any stipulations for those venturing into wildlife territory? It also poses an ethical dilemma, should man be allowed to blast anything that evokes a fear response in him just so he can take a walk through the park? How are we to separate men defending their lives from cowards hiding behind a gun?
One of the difficulties is that there is no sure way of knowing whether or not that bear or moose is really going to run you over or veer off into the brush short of standing there and letting the animal decide.
I have bear and moose literally just outside my front door; often see them multiple times daily. My closest non-hunting bear encounter was at about 4 feet.
Hunting and defense are completely different situations. I am amazed at all of the folks who think that they are going to be safe with a (list you favorite caliber here in hand gun or rifle) or with the "you just need to have good shot placement" crowd, or the "I will just keep shooting and empty xx number of rounds until it stops" when considering a charging bear. (Sure these things can help, but they do not make one safe.)
Bears can run in the neighborhood of 40mph; just imagine reacting to a bear popping out of the brush 30 feet away that can run 40 mph and can weigh a half a ton or more. In the couple of seconds that you might have, somehow multiple rounds, shot placement, and caliber are not as reassuring as they are sitting behind a keyboard.
Check the numbers, do some real research, and/or live where you can observe them, I have, and my first response is bear spray, backup shotgun with slugs (or magnum hunting rifle), and final back up 10mm in that order when I am out in the bush. (Just outside my front door: spray and backup 10mm.)
The "Bubbas" referred to above are unfortunate and everywhere. Help educate those that can be, make a difference.
YMMV