I call bull. That is collectivist thinking, individuals are not responsible for the actions of others.
We are somewhat responsible- if we voted for- when it's an elected official that goes off the reservation. It's our duty to elect people that will uphold the office with integrity and the best interests of the people and nation (I know, very ideological, but ultimately, that's what we want, right?).
I do not accept responsibility for anything that happened before my time, nor the transgressions of our elected officials I neither voted for nor endorsed.
But back on topic...
My saying is "a person is smart, people are dumb." If you allow the general populace equal access to weapons and machines of war as the government, you will reign down a s**tstorm of grief so fast, you'll be glad the nuclear winter will kill you soon enough.
We have a hard enough time keeping guns from criminals. Let's be honest: we
can't keep guns out of the hands of criminals. It's logistically impossible to do this without locking down the general public. Do you think it would be easier or harder for a criminal to obtain worse weapons if they were available? Do you think criminals would target worse-weapons of war? Do you think the handful of successful and legal-but-integrity-less people would purchase the worse-weapons and sell them to unscrupulous people, taking the money and running to a private, non-extradition country/island?
Imagine the wrath of some woman who is driving a tank, who goes through a drive-thru and finds out there's no chicken nuggets left. A scout leader who trips over a stump while carrying a loaded RPG, who ends up killing the troop, and himself, with his mistake. Screwing up with a gun usually affects one person directly. Worse-weapons of war will impact many more. While I'm not opposed to thinning the herd, I am against it when my color-blind neighbor makes his First Dirty Bomb from a Harbor Freight mail-order kit.
There is no benefit to the general populace to own worse-weapons of war other than to have an equal d**k-measuring contest with the government. The risks greatly outweigh the reward.