"The fact was patent, and rather, interesting when considered in connection with the horror rebels express at the suggestion of black soldiers being employed for the national defense." Again, if black combat soldiers were common in the confederate army then why the revulsion at the thought of black Union combat soldiers? The clear explanation is the thought of any black combat soldier, North or south, was offensive. So the blacks Dr. Steiner saw were supporting the army, not a part of it.
You've inverted the meaning of his statement, by force majeure practically, to fit your a priori position that a) Southerners were (are) total racists and bigots (and fill in the rest), and so therefore b) they were incapable of doing/countenancing x. They can't have put up with x, and so therefore someone's direct observation of x must have been mistaken.
The quotation is, from your own post, "The fact was patent, and rather, interesting when considered in connection with the horror rebels express at the suggestion of black soldiers being employed for the national defense." Well, what fact is that? "over 3,000 negroes had arms, rifles, muskets, sabers, bowie knives, dirks, etc. And were manifestly an integral portion of the Southern Confederate Army."
Doesn't get plainer than that, N-S. They were armed. They were traveling with the army, and they were armed as soldiers. How do you get to the idea that they can't have been soldiers because my a priori argument won't allow them to have been? That is what I read in your posts, over and over again. I think it tokens a major inflexibility in your thinking. AKA "bigotry" -- the unwillingness (per the dictionary) to reconsider opinions in the light of new evidence. I'm considering, but you refuse to.
And for the difference in Southern attitudes toward black soldiers, if that's what they were (and it sure sounds like it, from the good doctor's observation), there is the simple matter of the difference between our'n and Mr. Lincoln's army which, if it contained formations of black soldiers, would have replicated in fact, in cold hard concrete facts shod with steel, the avenging army that John Brown wanted to unleash on Virginia and the South when he seized the arsenal at Harper's Ferry, not to preoccupy it, but to arm the slaves for a bloody, Nat Turneresque, Dessalinesque mass rising that would sweep away slavery on a flood tide of major massacres of Southerners -- Haiti writ large. I would tend myself to rather disfavor that kind of outcome for the South.
How reassuring to the white Southerner, then, that his own Negroes (and we don't know whether these were slaves, freedmen, free blacks, or all three) would serve in the army, as servants or as volunteers, and not in that other army.
As I said before, I would like to see more recovered evidence. But your position would seem to be that you don't -- that you know the answers already, and that you would prefer not to be disturbed in your opinions about the South and Southerners. You'd rather stick with the political caricature Martin Luther King marketed about Southerners. You wouldn't believe a used-car salesman, but you'd believe a political agitator's "truth", his action message, over the evidence of your own eyes, or in this case the word of an eyewitness. The South wasn't what Martin Luther King said it was, except when you poked it with a stick and called it names. And yet you seem to require what King needed, that the South be all bad, all the time. That is a caricature, and a caricature is a kind of lie by exaggeration, like Michelangelo's "David".