Margaret,

Whatever the GAR chose to deny in 1891, the fact is officially sanctioned deliberate mistreatment of Southern POWs certainly occurred at Camp Morton (though this prison was not the worst)
To put this in a larger context consider this: 193,750 Union and 215,000 Confederate soldiers, became prisoners of war. More than 30,000 Union and 26,000 Confederate prisoners died in captivity, which equals 12% in the North and 15.5% in the South (at least if you believe federal statistics). While it is true the CS lost more of it's prisoners than the US it must be remembered that this was in a Country in which women and children were starving. It stands to reason that the federal government, with their vastly superior resources of food, transportation, housing, population, medicine, and medical personnel should have lost far fewer of their prisoners. How could a 12% death rate under such favorable conditions be accounted for other than by deliberate abuse on a wide scale?