Exactly, blacks fighting with white in the southern frontier was not a new thing. The whole southern culture was in fact whites and blacks working side by side on a day to day basis. Just because the whites has a position of authority does not mean the working relationships and even respect was not developed between the two races.
And old man once said to me a long time back that the difference between the North and the South as they relate to the negro was that the Southern looked upon the individual negro and judged him accordingly and disdained the race, while the North looked upon the races approveingly while disdaining the individual Negro.
After the Civil War the Northerner certainly didn't want the negro to live beside them in their cities. While in the south it was a common thing.