I am sure there was some cruelty at Andersonville, I would be a fool to say there was none. The difference is the North had food and medicine the South did not. There was just no need for what the North did. I have researched the northern prisons for graves and found a lot of cases of abuse. I came to the conclusion that this abuse was mainly for the entertainment of the prison commander and guards. Bear in mind I have not researched the Southern prisons.
I could be wrong but I believe the only person tried of war crimes, was the commander of Andersonville. No Northern commander ever had charges brought against him.
If you would like links so that you may read these stories, I will attempt to look them up and post them for you.
George