In all there were about 195,000 southern men who fought for the North, about half of them white. While there were units like 1st Arkansas Cavalry and 1st Alabama Cavalry and 1st North Carolina Infantry (where the murdered POWs were from) in the Union army I don't recall coming across a 1st Ohio or a 1st New York Cavalry or a 1st Vermont Artillery in the confederate army. Maybe that's because the rebellion didn't enjoy the overwhelming popular support sothron supporters like to believe it did.
From the article at the header:
Northern occupation forces at first tried a policy of conciliation, hoping to win the Southern whites back to the Union. When this failed, they moved toward a harsher policy here as they did elsewhere, confiscating the property and liberating the slaves of people they now perceived as enemies to be crushed rather than deluded victims of secession conspirators to be converted.
Wills does not make a big point of it, but his findings stand "in sharp rebuttal" to the arguments of historians who portray a weak or divided white commitment to the Confederate cause as the reason for defeat. "These people sought to secure victory until there was no victory left to win."
Did you forget that point in the article? Or do you just disbelieve it, because polemically it is ever so much more elegant to say, "you see, even your side didn't believe in your palsied, unworthy cause"?
What imagined crimes? They were guilty of desertion and high treason, of bearing arms against their sovereign States and the Confederacy. They got the same thing that John Walker Lindh deserves, and which the San Patricios got in 1847. Ben Butler would have done the same, but he and other South-hating red-hots were restrained for purely political reasons first by Lincoln, and then by Andrew Johnson and U.S. Grant. The Black Republicans made a lot of noise about hanging the Confederate commanders, but never got the office they needed to make good on their intentions.
Before they were Union soldiers, they deserted from the Confederate Army. Historically, desertion in time of war was (and still is?) punishable by death, so Pickett seems to be within the rules of war here.