I think the Confederacy should be condemned for its insistence on upholding slavery, but not that it should be treated as pure evil. It's not as if many of the colonial leaders we most glorify weren't firm defenders of slavery themselves. Not even counting men such as Jefferson or Madison (who were lukewarm on slavery), if you claim to admire Washington, Jackson, or Patrick Henry in one breath and then condemn all slaveholders in the other and demonize the Confederacy for such, just be aware that there's a discrepancy that you need to be aware of.