If a bear’s just out minding its own business, then pretty much any response from a human other than screaming and running away will make it back down. Sure, it knows it can probably take you, but it also knows that you’re likely to put up a fight and be more trouble than you’re worth.
But if, for instance, the bear thinks its young are threatened, then no show of force is going to be enough to stop it, short of either a very lucky or very powerful shot.
And the difficulty is that you have absolutely no way of knowing which is which, for any given bear you might meet.
Too late in the year for mom to give a shit about her teenaged cubs. “Are you two still here? Go look for your father. He won’t care, either, but you’ll be out of my hair.”
I used to have a crow that would hover around the yard (looking to steal chicken eggs- I took care of that fool!) and it would freak the wiener dogs out. They would run around chasing it, thinking they had a shot.
Dachshunds are the most comical of all dog breeds.
My brother’s dog was freaked out by a blimp. It was the Fuji blimp, IIRC. She just kept running around in circles, barking, and looking up at the sky. It was pretty hilarious. She must have thought it was the end of the world.