If your argument is that he had the right to confiscate anything used in the war effort, why didn't he confiscate their horses, or their cattle, or their homes, or whatever else was used? If the purpose is to confiscate in defiance of due process, why is this one so narrow?
Sounds to me like it wasn't about military purposes at all, it was simply what he preferred to do, and is therefore not a legitimate use of that power.
Making it discretionary makes it dictatorial.
The Confederacy also had confiscatory policies, if I am not mistaken.
He did in fact confiscate their houses, their horses, their mules, their cotton, their cattle, hogs, chickens, their wheat and their corn. Read what Phil Sheridan did in the Shenandoah valley or Sherman through Georgia in 1864. They destroyed or confiscated anything of use to the Confederate cause. Not selectively or optionally, all was destroyed or confiscated. The term for it now days is total war.
Both sides confiscated "contraband", "contraband" defined as pretty much anything of value to the war effort and that certainly included the items DiogenesLamp lists here, plus others.
Neither side used "due process" as DiogenesLamp defines it, meaning a court hearing.
I would be most interested to see quotes from DiogenesLamp where anyone from the Civil War era thought such "due process" necessary.
Confederate armies in Union regions confiscated everything they could and destroyed any "contraband" they couldn't take with them, i.e., railroad bridges.
Sometimes they did pretend to "pay for" things they took with inflated Confederate money, but not that often.
Confederates also took Northern freedmen as slaves for sale in Confederate slave markets.
By contrast Union armies normally lived off their own supply trains and did not molest local civilians for food & other necessities.
And when that policy changed (i.e., Sherman in Georgia) it became a matter of controversy lasting centuries.
But nobody then or now much remarked when Confederates did it.
"Democrats will be Democrats", I think is how they put it.