I have no experience with any kind of bear so I'll assume you know lots more about them than I do. With that, let's look at it from a different angle - The man and his dog were lawfully where they should be. Now, the bear being a wild animal and all, was just doing what bears do so in that regard none of the three involved were doing anything wrong. Of course, one might suggest the bear was trespassing but what do bears know of trespass laws? That is, until one of them made a furtive move. Sure, the dog snarled and brought this move on. But, damn, isn't that what dogs do? Isn't that one of the reasons lots of us have dogs; so they can warn us of possible danger? I didn't pick up on the part of the story saying the dog attacked the bear if that exists in the writings. No, it says the dog growled and then barked. THEN the bear elected to make his move. Was he running toward the dog or the man? I can't tell because I haven't heard the bear's side of the story or that of the dog. Would a reasonable person see the bear's movement as threatening? Maybe. I don't think I'd want one running at me. What if the bear was actually running towards the dog? Would the man be within his rights to stop the bear from harming his animal if he reasonably believed that was the bear's intention? What if it were a calf, a goat, or even a comfort emu instead of a dog? I feel like the man would have that right. I also feel like the man would have the right to stop a perceived attack by any creature if he reasonably believes an attack is in progress.
The bear could have ran the other way. But, he didn't. He seems to have chosen to run toward the man and the dog. Do all bears act the same way in any given set of circumstances or are there some nuances of difference in bear behavior? I don't know but I bet you might. I think it's great that you chimed in here and have lots of experience with bears. Your continued commenting on this matter has the potential to educate us all.