Too easy to pick apart their argument
They are 8th graders in law school?
If these kiddos want to make Constitutionally-guaranteed rights subject to a cost/benefit analysis, then let's marshal the wisdom of Madison in Federalist #46, where he tackles the fear of a Standing Army. In 46, Madison basically says THE check against a Standing Army turning against the citizens is - wait for it! - the militia:
The only refuge left for those who prophesy the downfall of the State governments is the visionary supposition that the federal government may previously accumulate a military force for the projects of ambition. The reasonings contained in these papers must have been employed to little purpose indeed, if it could be necessary now to disprove the reality of this danger. That the people and the States should, for a sufficient period of time, elect an uninterupted succession of men ready to betray both; that the traitors should, throughout this period, uniformly and systematically pursue some fixed plan for the extension of the military establishment; that the governments and the people of the States should silently and patiently behold the gathering storm, and continue to supply the materials, until it should be prepared to burst on their own heads, must appear to every one more like the incoherent dreams of a delirious jealousy, or the misjudged exaggerations of a counterfeit zeal, than like the sober apprehensions of genuine patriotism.
Extravagant as the supposition is, let it however be made. Let a regular army, fully equal to the resources of the country, be formed; and let it be entirely at the devotion of the federal government; still it would not be going too far to say, that the State governments, with the people on their side, would be able to repel the danger. The highest number to which, according to the best computation, a standing army can be carried in any country, does not exceed one hundredth part of the whole number of souls; or one twenty-fifth part of the number able to bear arms. This proportion would not yield, in the United States, an army of more than twenty-five or thirty thousand men. To these would be opposed a militia amounting to near half a million of citizens with arms in their hands, officered by men chosen from among themselves, fighting for their common liberties, and united and conducted by governments possessing their affections and confidence. It may well be doubted, whether a militia thus circumstanced could ever be conquered by such a proportion of regular troops. Those who are best acquainted with the last successful resistance of this country against the British arms, will be most inclined to deny the possibility of it. Besides the advantage of being armed, which the Americans possess over the people of almost every other nation, the existence of subordinate governments, to which the people are attached, and by which the militia officers are appointed, forms a barrier against the enterprises of ambition, more insurmountable than any which a simple government of any form can admit of. Notwithstanding the military establishments in the several kingdoms of Europe, which are carried as far as the public resources will bear, the governments are afraid to trust the people with arms. And it is not certain, that with this aid alone they would not be able to shake off their yokes. But were the people to possess the additional advantages of local governments chosen by themselves, who could collect the national will and direct the national force, and of officers appointed out of the militia, by these governments, and attached both to them and to the militia, it may be affirmed with the greatest assurance, that the throne of every tyranny in Europe would be speedily overturned in spite of the legions which surround it.
Thus, while I certainly am no fan of the innocent loss of life, Madison would likely want these Yalies to weigh the 'cost' of 'gun violence' against the benefit of 300 million firearms and trillions of rounds of ammo in the hands of the citizenry. My guess is Madison, likely also no fan of the needless loss of life, would agree with Joseph Story who said:
The right of the citizens to keep and bear arms has justly been considered, as the palladium of the liberties of a republic; since it offers a strong moral check against the usurpation and arbitrary power of rulers; and will generally, even if these are successful in the first instance, enable the people to resist and triumph over them.