Although this account of black slave-soldiers is really grasping at straws, it is true that free blacks in the south fought for the Confederacy. I still remember a news report that featured a very dark black man who was quite furious when the State of Mississippi was considering getting rid of the Confederate flag which made up part of the state flag. His great-grandfather had served with distinction in the Comfederate Army and he was every bit as angry as the white descendants of Confederate soldiers.
A number of free blacks owned slaves themselves, of course. Half of the free blacks in the US in 1860 lived in the South. The first person to die during John Brown's takeover of the Harper's Ferry arsenal in 1859 was a free back telegraph operator who was killed by Brown's followers for attempting to notify Washington DC of the siezure.
And just about all of the slaves.