The sale of explosives is quite regulated, presently, as is the sale of firearms in many states. But consider what you are really saying when you support denying firearms & explosives to people on a "terrorist watch list." They are only on that list by the fiat of some federal bureaucrat or someone in the executive branch. Like the people on the No Fly list. These are people against whom there is insufficient evidence to make a criminal case, so instead they are extra-judicially punished. That's how crazy it's gotten.
The other problem with your post is that if you resent expansion of second amendment rights (it's not originalist! The Founders meant militia!)--and they have only been expanded to the point that it is unconstitutional to ban firearms outright or require them to be inoperable--then how do you feel about the heavy reinterpretation of the fourth, fifth, sixth, and fourteenth amendments that occurred during the civil rights era? It would be difficult to argue that the original intent of the constitution assumed the inherent coerciveness of custodial interrogation (of course, Miranda may be on a path to be reinterpreted back into oblivion), or that the fourteenth amendment originally precluded segregation (or, hypothetically, allowed gay marriage). The originalist argument for expansion of the second amendment is likely stronger than in many of those other cases.
Your argument amounts to "I resent the expansion of the amendments that I don't like," and "I resent giving equal rights to people that I don't like."