Can we start the discussion from this initial premise? Unlike a technology such as the car, which has a purpose other than crashing into things when in control of drunk drivers, you posit that the gun's primary purpose is death.
From this follow two premises:
1) Controlling the distribution of firearms controls the amount of death capable of being distributed in a society.
2) The entity who controls said distribution as well as being in possession of the largest quantity of weapons has a monopoly on life and death.
In the first case, the natural question is whether everyone should have an equal right to distribute death, or indeed if an equilibrium is even possible. Clearly there are price and access barriers to gun ownership that have little to do with regulation, disadvantaging people from engaging in the market for this supposedly "equalizing" force. Those who can afford more/better weapons or who are willing to acquire them at cut rates through illicit channels are thus given greater access to making death. This is anything but equal. Further, in a conflict, the grievances of those in possession of firearms is privileged, not made equal to their counterparts. The gun is a symbol that usually means "I am in control," during confrontation, because of its implicit ability to bring death. That is called biopower (by Foucault at least).
Biopower has historically been vested in the state, making it the only credible arbiter of who may live and die. The social contract we all subscribe to hands that power over to the state as justification for why it can provide for the common defense and adjudicate who must be removed from society for violating the rule of law. To distribute this power too widely in a society is to invite anarchy or at least make arbitrary the rule of law. Monopoly over biopower is what makes the state the state. In a democracy at least, the idea is that there are other technologies at our disposal for bringing about equality besides those that invoke death. We outsource control over biopower to the state in exchange for its protections. It follows that the fairest state is the one which permits the least amount of death. That was the historical project of the state. Today we focus more on the quality of life of those who live within the state, which of course relates to ameliorating the death drives of those who are socially aggrieved or psychologically damaged.
So it's hard to see the equalization power of the gun in the context of the society we've organized. Other than being an often repeated cannard, that statement seems like an artifact of an earlier, less stable time in Western civilization that hasn't existed for more than a century perhaps.
