The Confederacy was illegitimate and an attempt to overthrow the government of the United States and replace it so they could continue a way of life that was no longer deemed acceptable. Once the South surrendered they should have been forgiven for the traitors that they were and re-assimilated back in to the United States and their previous military exploits forgotten about as it was enough that they were forgiven to begin with. Celebrating their military service ignores the fact that they were traitors to the United States of America and they were lucky enough to be taken back in. They didn't engage in military service. They attempted to overthrow the government.