Slavery was ancillary to the main conflict of the Civil War, which was really about state's rights. The Emancipation Proclamation was made to stop Britain and other countries from aiding the Confederates, by stigmatizing them to a major degree in the international community. If anything, #6 on this http://listverse.com/2013/03/17/10-war-crimes-of-the-us-civil-war/ would set me off.
I live in the South, and I'm saturated with a great deal of apologetic statements that attempt to downplay both the role of slavery in the war and the true sentiment of the South.
Unfortunately, the ugly truth is as futile to try and hide as the World War 2 Germany was for the Holocaust deniers.
I don't know how different I'd be if I had been raised in that time period, but I know that if it came to it now, I'd be against the side that wished to continue treating humans as property.