Oh how the revisionists like to quote Fredrick Douglas…bet you won’t hear this one.

"…Rising above vulgar prejudice, the slaveholding rebel accepts the aid of the black man as readily as that of any other. 

If a bad cause can do this, why should a good cause be less wisely conducted? We insist upon it, that one black regiment in such a war as this is, without being any more brave and orderly, would be worth to the Government more than two of any other; and that, while the Government continues to refuse the aid of colored men, thus alienating them from the national cause, and giving the rebels the advantage of them, it will not deserve better fortunes than it has thus far experienced. 

Men in earnest don't fight with one hand, when they might fight with two, and a man drowning would not refuse to be saved even by a colored hand." (Foner, Volume 3, pages 151-154) FREDRICK DOUGLAS 

Lincoln never wanted to use black troops until forced to by political pressure and the Federal Army, unlike the Confederate Army remained segregated until 1950 during the Korean War.