I agree with most of your post. Furthermore, I would go so far as to say that the author of original article is in error when stating that a U.S. Declaration of War must be based on an overt act of war by another nation. While it might be unwise to do otherwise in most cases, I see no legal or Constitutional requirement for it.
However, it is incorrect to state that there was no Declaration of War against the Barbary pirates. A Declaration of War against the Bey of Tripoli was passed on February 6, 1802.
Simply because your post mentioned the Barbary Pirates and it is educational for everybody else to see how the Founding Fathers interpreted the Constitution that they themselves drafted and ratified.