Even making the dubious assumption that the need for a militia has been supplanted by the fact of a standing army, the author mistakes reasoning for a requirement. The amendment clearly reserves a power to the people, not the government. The amendment does not say, "The right of the people to keep and bear arms shall not be infringed, [b]so long as[/b] a well regulated militia is necessary to the security of a free state." The right of the people is not conditioned on the need for a militia. The need for a militia provides a good reason for the right of the people, but it is not a requirement. And, while it is arguable that the change in times and the fact we now have a standing army may obviate the need for a militia (a point which I do not necessarily concede), the change in the structure of the armed forces does not make the right any less effective. Take the third amendment, for example. While many scholars would argue that it is no longer enforceable and a historical artifact, it is only because of the structure of the armed forces today that makes it irrelevant. It is still quite enforceable should the army decide to quarter troops on your lawn. It is just never used because of the structure of the armed forces today; the right, however, still exists.
In fact, had this mindless doofus done his homework, he would have realized the entire BoR are protections against the federal government. It would have been sloppy writing indeed if the Founding Fathers had provided ten amendments, nine of which (and in no particular order) were to protect the people and the states against the powers of the federal gov't. Additionally, while we do have a standing army today, any male of proper age can be drafted, not unlike calling forth the militia in 1791. Thus, every able bodied person who could be subject to the draft can be thought of as a "reserve" part of the standing army, or the militia.