One Man’s Response
The myth of the black Confederates 
Washington Post (blog)
The War was not fought over slavery — it was fought over taxes, specifically the Morrill Tariff. Had slavery been the issue, the States needed only ratify the Corwin Amendment to make slavery permanent.
That blacks, both bond and free, served the Confederate cause is well-documented, and the evidence is not hard to find if looked for.
Happens that the first US army officer to die in battle, Major Theodore Winthrop of Massachusetts, was shot at Big Bethel by a black Confederate sniper.
The Washington Post would do well to practice responsible journalism rather than shooting its mouth off inaccurately.
Clifton Palmer McLendon