A standing army we shall have, also, to execute the execrable commands of tyranny; and how are you to punish them? Will you order them to be punished? Who shall obey these orders? Will your mace-bearer be a match for a disciplined regiment? In what situation are we to be? The clause before you gives a power of direct taxation, unbounded and unlimited, exclusive power of legislation, in all cases whatsoever, for ten miles square, and over all places purchased for the erection of forts, magazines, arsenals, dockyards, &c. What resistance could be made? The attempt would be madness. You will find all the strength of this country in the hands of your enemies; their garrisons will naturally be the strongest places in the country. Your militia is given up to Congress, also, in another part of this plan: they will therefore act as they think proper: all power will be in their own possession. You cannot force them to receive their punishment: of what service would militia be to you, when, most probably, you will not have a single musket in the state? for, as arms are to be provided by Congress, they may or may not furnish them.
Let me here call your attention to that part which gives the Congress power "to provide for organizing, arming, and disciplining the militia, and for governing such part of them as may be employed in the service of the United States--reserving to the states, respectively, the appointment of the officers, and the authority of training the militia according to the discipline prescribed by Congress." By this, sir, you see that their control over our last and best defence is unlimited. If they neglect or refuse to discipline or arm our militia, they will be useless: the states can do neither--this power being exclusively given to Congress. The power of appointing officers over men not disciplined or armed is ridiculous; so that this pretended little remains of power left to the states may, at the pleasure of Congress, be rendered nugatory. Our situation will be deplorable indeed: nor can we ever expect to get this government amended, since I have already shown that a very small minority may prevent it, and that small minority interested in the continuance of the oppression. Will the oppressor let go the oppressed? Was there ever an instance? Can the annals of mankind exhibit one single example where rulers overcharged with power willingly let go the oppressed, though solicited and requested most earnestly? The application for amendments will therefore be fruitless. Sometimes, the oppressed have got loose by one of those bloody struggles that desolate a country; but a willing relinquishment of power is one of those things which human nature never was, nor ever will be, capable of.
Please realise that Henry was specifically addressing Article 1, Section 8, Clause 16 in responding to this question. He directly quotes that passage. I've highlighted that since I am pretty sure you would miss that bit if it weren't in bold, underlined, large print.
Also realise that this passage supports the civic interpretation of the Second Amendment and any essay supporting a right to arms outside of the militia context will have to overcome that hurdle.
OK, if firearms were commonplace, why is Henry worried that the Federal government would fail to arm the militia? Wouldn't that hint at scarcity rather than abundance? Also, by having the issue framed as failing to arm militia rather than confiscation, doesn't that also hint at the issue being provision of arms to the militia?
If you wonder why I find the civic right interpretation far more credible than an individual right outside of the militia context, it is because I have yet to see an explanation of the non-militia right that does not address these historical FACTS.