I've seen this behavior, but I do not have reason to think it is related to any concept of firearms.  I'd call it 'recognizing predatory behavior'.  I used to keep goats and raised up to 100 kids per year.  To sell breeding stock, I listed photos on a website.  It was amusing, and frustrating, to see how some (not all) of these goats would go into full panic when I'd point a camera at them and raise it to my eye.  Some would even scream as they ran away.  However, I could get good photos of them by shooting from the hip.  Apparently shooting from the hip is not predatory behavior?    Similarly, I've noticed that some coyotes lolygag in the camera's IR while it's recording video and other coyotes are startled and scramble away.  I've also been with a group of 4 people watching 2 bull moose.  Neither our side-by-side approaching nor getting out and talking bothered the moose.  Squeezing an empty water bottle sent them running.  

I think you overestimate their fear of guns.   It's not the gun, it's the person holding it.    SCARED people with guns are dangerous, unpredictable, volatile.   Calm, confident people with guns are just calm, confident people .. not a threat.   It's the fear that turns the gun into a hazard.   Humans telegraph fear quite loudly in our posture, motions, and so on.    I've had a couple of sightings, camp visits at night, been punked / messed with .. and every time, minus one, I had a gun, often a hunting rifle slung over my shoulder, not something hidden.    It ain't about the gun, it's about the human.

I have always believed they think anything held by a human is a gun. 

@Daniel Perez 

No doubt, and despite the fact that nobody can definitively say what it is there’s still no shortage of people flippantly dismissing it as a bear because the idea that it could be something else is one they don’t want to deal with.  Just like Patty is a guy in a suit, sure…..