Unfortantly Camp Douglas was not the only union prisoner-of-war camp that mistreated Confederate POWs. Mistreatment was the rule, not the exception.
If you have not already done so, go to www.izzy.net/~michaelg/14ms-1.htm and read Pvt Milton Ryan's (Co B, 14 MS Inf) memories on how he was treated at Camp Douglas, and at Camp Chase, Columbus, Ohio.
Union POWs actually had a better chance of survival than Confederates.
My GG Uncle Amos Carter, Co D 14 MS, was KIA at Ft Donelson on 15 Feb 1862. GG Uncle Jacob Carter, Co D 14 MS, was wounded in action 15 Feb 1862 and sent home to recover (in other words, they did not expect him to live). He did survive, but was discharged due to his wounds in Mar 1862.