Or would a more accurate explanation be that those blacks seen with the confederate army were only there in a supporting role? That they were servants and teamsters and laborers, roles that they traditionally played in southern society? And that that the idea of facing armed black men in combat, as equals, was totally foreign to the average confederate soldier and that was what they found horrifying?
Very many were, that is true. However, very many fought as soldiers. They fought like hell and killed many a Union invader. Northern Republicans and Union army veterans testify to that truth.
...And that that the idea of facing armed black men in combat, as equals, was totally foreign to the average confederate soldier and that was what they found horrifying?
Nah. My previous explanation is the correct one. That feeling of betrayal and the outrage born of it was expressed in many diaries and letters of the time.