The term "employ negroes in war," as used throughout the Military and Naval Laws, as well as the Acts of Congress which established them, included not only duty as soldiers, but also duty as "civil service" employees, as you euphemistically called them, i.e., teamsters, fortification workers, etc. When referring specifically and exclusively to colored soldiers, the term "in arms against the Confederate States" was used.

The Confederate Congress held the opinion that the "employment of negroes in war," that is, in any military capacity, was a violation of the "laws and usages of war among civilized nations."

We're not answerable for the policies and actions of our Confederate ancestors, but in fairness to history it should be understood that the reasoning behind the Confederate position was that the employment of negroes in war might cause a "servile war" which "would, if successful, produce atrocious consequences." Such insurrections are the nightmare of slave-holding societies, and it should be noted that history is replete with examples of the atrocious consequences, from the slave revolts of the Roman Empire to the slave uprising in Haiti.

But it serves no purpose to roundly condemn nor leap to defend the policies of a long-dead government. History is what it is.