Let's remember that the Civil War, at its core, was about those southern states wanting to keep their slaves (to stay very rich) and ignoring the basic tenants of the United States Constitution:
“We hold these truths to be self-evident, that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the Pursuit of Happiness.”
So the leaders of the southern movement were a bunch of rich white men who didn't want to give up their free labor, and who convinced thousands and thousand of young men through BS propaganda (sound familiar?) that it was some sort of noble cause that made killing other Americans justified.
Lee, at various points during his military career, instructed his troops to capture any free blacks they came across and to return them to the south so they could be enslaved again.
When you have some time give this a read. Again, sound familiar?
https://en.wikipedia.org/wiki/Lost_C...he_Confederacy