Southern historians are guilty of D. when it comes to the Southern view in some cases but I think they are more accepting of the flies in the ointment for the Southern cause. Shelby Foote is one of the few that I have read who seems to have been fair in finding flaws (and can explain them) in both sides but he's not the only one. For a historian to dismiss something that has a negative impact on the winning side isn't just done in the CW.
For those of Southern roots, we see the same thing about our history written that the children of Japan and Germany see about theirs by those from the 'Other side'. Our own historians are more forgiving or give another explanation for actions deemed 'wrong' by the winner whiile the OR reports may be missing in some detail on the Union side. That's nothing but human nature.
Mark gave a couple of examples and I don't have reason to doubt their accuracy. Unless a 'real' historian can find positive proof that it wasn't so, I'd stand with the 'eye witness'. I base that on not only what I've read on Point Lookout, but other Federal prisons. We accept the conditions at Andersonville and that is our cross to bear even though there are some very valid points to make on the conditions found at that horrible place. Shame that can't be said for the other side. They did away with the evidence so to speak and used the old prison land for other things in most cases. We do however, have letters and other reports to support them from the Confederate prisoners on their conditions. If the prisoners were allowed to go hungry and cold when food and warmth was provided but not used by the Commanders of the prisons it is every bit as brutal as the story from Pt Lookout.