>What I don't understand is why they don't understand that.
Propaganda. Miseducation. Appeals to emotion. The usual totalitarian work. But don't think these tactics only work on the "left". We're all being played.
What they understand, that you don't, is that arms are not the only means to resistance and that they are not a particularly effective one at that.
Furthermore they are watching the Black Lives Matter movement (which you apparently have never heard of) and how the 2nd Amendment Crowd (not all, but probably most) is responding by expressing their support for state violence.
Personally I'm not a fan of gun control (guns are overrated) but I also laugh at suggestions like yours in light of how subservient and ingratiating the 2nd Amendment zealots are towards the police and military.