Unfortunately, Andersonville doesn’t actually stand out in it’s depravity, Union prisons were just as bad sometimes, but not as publicized.
The CSA had some excuses for poor conditions in its POW camps. The North had none. And the North treated black refugees fleeing slavery with savage indifference, and overt hostility, bordering on genocide. Those here who decry the deliberate devastation policies in the Shenandoah Valleys and elsewhere wouldn't know real evil if it kissed them. Read:
Sick from Freedom: African-American Illness and Suffering during the Civil War and Reconstruction by Jim Downs.
http://www.amazon.com/Sick-Freedom-African-American-Suffering-Reconstruction/dp/0199758727/ref=tmm_hrd_title_0