I think the bigger picture, beyond why the southern states seceded, is simply that they seceded and the Civil War was fought over their right to unilaterally do so. Even if you want to make the argument that the Confederacy wasn't merely pro-slavery, you still have to acknowledge that it was pro-secession.

So the remarks you've quoted here seem really odd, because it's one thing to respect the Confederate forces, but to agree with their cause goes beyond mere minarchism to full-blown sedition. Mind you, I never get the sense these guys really feel they're under an illegal occupation by a brutal regime. But I don't see how else it can be construed--either you think South Carolina still has a right to be independent of the US government, or you don't.