Why would Confederate officers petition their Congressmen to consider enlistment of black soldiers? How could they not know about the thousands of black Confederates claimed to be in Southern ranks? Were they colorblind?
There are plenty of service records of Confederate officers who applied to command black troops once Congress acted in March 1865. Why are there none in service records before the end of the war.
At least Dr. Williams cites sources, so in two of three cases we know they don't hold water. It makes no sense whatsover to cite either Horace Greeley, editor of the New York Times, or Frederick Douglas, life-long abolitionist, as authorities on Confederate soldiers.
When were either one of them within a hundred miles of a Confederate army in the field? Did they use a crystal ball to somehow gaze into the ranks of Southern troops? What other supernatural powers did these two men possess? Horace Greeley or Frederick Douglas or anyone else would make good sources of events they witnessed first-hand, but not of far-away events and people they never met. It's like not accepting your word about your home town, but believing everything written about it by a famous news reporter who never left his office in a far-away city.
Wouldn't it make more sense to cite a Confederate officer on the racial composition of his command? Do you suppose that an officer who knew his soldiers by name from home might know more about them than a popular writer in a distant Northern city who never laid eyes on any live Confederate?