Liberal positions on firearms have almost universally been wrong. (perhaps the only correct ones are the vigorous enforcement of existing gun laws and restricting access for mentally ill people).
Now looking at the deterrent value of nuclear weapons and applying this to firearms is certainly valid. The difference is mostly in scope, but another critical difference is that nuclear deterrent centers around the MAD doctrine which ensures complete and utter destruction of BOTH parties. IOW, if you attack me with nukes, you die too.
Not so with firearms; the MAD principle doesn't apply. The person being attacked has a much better chance of surviving the encounter than the attacker.