The core cause of the civil war was slavery. Every other cause or bullshit justification just leads back to the abolition debate. A lot of southern schools teach otherwise in an attempt to avert the justified shame they’d otherwise feel, but the core cause of the Civil War was slavery, and there is no other cause of that war that’s independent from Slavery.
Confederate soldiers who willingly fought for the independence of the confederacy were fighting to preserve slavery, no matter how you slice it.
Wearing or flying the confederate flag with pride is taking pride in a culture built on slavery, no matter what bullshit rationalization about “states’ rights” they give you. The “states’ right” the confederacy was fighting for was slavery. One time someone told me that they were fighting for their “right to secede.” I pointed out to him that they were only seceding to preserve slavery, and promptly smacked him upside his head.