The sad fact for hunting is when somebody tries to take a large dangerous animal while obviously under-gunned and fails spectacularly it leaves a stain on the entire hunting community. If on video and the antis find it - will be played and re-played for ages. Stunt-hunts are just that - one could probably kill a Brownie with a spear but you won’t find me trying it. I will say, having been there, when within 50 yards of a fully mature Brown Bear Boar, the shear size and power of the animal becomes much more obvious, and thoughts begin shifting beyond not just making a killing shot but to putting and keeping him down.
In addition to rifle hunting I’ve bowhunted most of my life with numerous African Safaris under my belt, including dangerous game. Folks have already pointed out that a well-placed arrow will very efficiently kill. While that’s true, the arrow needs to penetrate to and through the vitals.
Having taken multiple DG game animals via an arrow (Cape Buffalo, Hippo, Water Buffalo, etc) I would never use a bow/arrow/broadhead setup seen as adequate for deer or elk for those critters. Commonly used a ~800gr arrow with a tool-steel two-bladed head.
What was very frustrating was having to overcome outfitter and game department concerns due to guys failing with inadequate equipment. One was a very famous TV personality who came South Africa to kill a White Rhinoceros with his Whitetail Rig. He failed spectacularly and literally porqupined that poor beast. Worse yet, it was all captured on video and used as anti-hunting propaganda for decades (scoured the web and could no longer find it as it happened decades ago). Don’t remember how many arrows were sticking out of that Rhino but I don’t believe it ever succumbed and had to be shot. This shut down or severely restricted all DG bowhunting for a number of years throughout many African Countries. Some are still in effect to this day.
In my hunting experience going after a mature Brown Bear Boar with a light cartridge suitable for deer and antelope is simply poor judgement. One might be lucky and get away with a single well placed shot, but if it goes bad it will likely go spectacularly bad.