It is just psychological. Idiot gun-grabbers see themselves and those around them as not being responsible enough to possess a firearm. They have a phobia of guns.
Yet, without a firearm, they retain the phobia about those that may possess a firearm. This pathology has an element of immature narcissism that projects this irresponsibility in everyone.
Therefore, everyone must be dis-possessed of firearms.
I think that rabid anti-military fanatics are similar. For them, the only reason to join the military would be to experience the joys of torturing, killing, and destroying without any fear of repercussion. Since that is their militaristic fantasy, they assume that everyone has the same fantasy and that those who join the military are acting out that fantasy.