I found an online book (limited preview) that is very detailed, highly referenced and intellectual on the subject of the Confederate Battle Flag and its post war history. Also...Black Confederates and their history. Very good reference material.

Its called "Racist symbols and reparations: philosophical reflections on vestiges of the American Civil War", by George Schedler, 1996.

Quote "Rather than compare workers and slaves, it might be more helpful to contrast the treatment white soldiers on the respective sides accorded their free black fellow soldiers. On this score, it appears that the treatment of the few black soldiers by Confederate troops was better than that the Federal troops accorded their black volunteers--- and it is the battle flag under which these few free blacks served in combat that is at issue here."

George Schedler --Chair and Professor, Philosophy Department, Southern Illinois University, Carbondale

http://books.google.com/books?id=Nb0sOtnBSXgC&pg=PA32&dq=the+graves+of+%22black+confederates%22&lr=&as_brr=3&cd=7#v=onepage&q&f=false