Conor Friedersdorf has a great rant against it:
I believe in an individual right to bear arms, and I have no problem with Americans who advocate on behalf of that right. If the feds start rounding up innocents to slaughter I have no problem with an armed citizenry fighting back. But folks who want to guard against a tyrannical government are foolish to focus on the 2nd Amendment while abandoning numerous others for fear of terrorism. The right to bear arms is the costliest liberty we have, in terms of innocent lives lost as an unintended byproduct; it is very unlikely to be exercised against the U.S. government in the foreseeable future; and its benefits are less important to securing liberty than habeas corpus and due process, as the experience of other free peoples demonstrates. I understand why people advocate on behalf of the right to bear arms, despite its costs; I don't understand why so many behave as if it is the most important safeguard against tyranny to maintain.