My question for you is why there is such surrounding controversy whether or not the scene may have been staged.  Paintings are/were commonly staged.  It is not unheard of for photographs to be posed/staged.  It is my understanding that this wasn't being used as propaganda but as a means of educating the general public.  Am I incorrect?  
I am, again, very pleased with the study of Civil War works.  I am fascinated by Civil War history.  I definitely agree that these photographs should be preserved.  Staged or otherwise, they communicate to the country and future generations a war they may otherwise never been able to adequately study.