The protection of civilians and their property has fluctuated wildly - from complete and utter destruction of belligerents in ancient times, to the recent policies of protection. Plunder and pillage was prohibited by the 1806 Articles of War. I do know that during the time frame in question this was instituted:
Art. 44. All wanton violence committed against persons in the invaded country, all destruction of property not commanded by the authorized officer, all robbery, all pillage or sacking, even after taking a place by main force, all rape, wounding, maiming, or killing of such inhabitants, are prohibited under the penalty of death, or such other severe punishment as may seem adequate for the gravity of the offense.A soldier, officer or private, in the act of committing such violence, and disobeying a superior ordering him to abstain from it, may be lawfully killed on the spot by such superior.
Instructions for the Government of Armies of the United States in the Field (aka The Lieber Code), 24 Apr 1863.
Or maybe it's an example of the poor scholarship DiLorenzo was known for in 2001. As I recall he was caught in quite a few falsehoods in those days.