Emotions are checked in some order. If an emotion is sufficiently excited, the rest of the list is ignored. For peasants, the emotion at the top is always fear.
When a non-peasant sees someone with a gun, they may think, "Ah, he has a gun, good for him I guess." Unless you were planning on antagonizing him, it's of little consequence.
When a peasant sees someone with a gun, they are afraid of the gun. And that's it. They are consumed by fear of the gun. They'll find themselves unable to appreciate anything else until the gun is removed from their perceptible environs.
This is why peasants like kittens. You can't possibly be afraid of a kitten. They can feel something other than fear in the presence of nothing but kittens, which is a nice change for them.
This effect is likely enhanced by living in democratic times. The local norm is cowardice. Bravery is enviable, so even the few individuals who are capable of it know better than to openly display any. The peasant's role models all act like cowards. He is never shown how the self-secure act; he is not genuinely aware that non-cowardice is an option. At best courage is a distant, abstract hypothetical vagueness.
This is particular bad when the peasant himself is holding the gun. He's
more afraid of his own tools than he is of the attacker. Not the best idea to give a coward a deadly weapon. The
irrationality of this is obvious even to the peasant themselves, and the
strain is apt to drive them nuts. Even if they manage to be strategically stupid and forget to be afraid of the weapon, they're still likely to panic due to being a coward who is under attack.
Perhaps it is sociologically prudent to discourage armament in democratic times. Only those who are willing to brave the frowns will arm themselves, ensuring few cowards adopt the habit.