Well, the libertarian movement is home to more than a few neo-confederates, so this isn’t entirely shocking.

They have many revisionist history tomes out there about how Lincoln was a tyrant that oppressed the South and how the South wasn’t really engaging in treason over the ‘right’ to own people, and it was all about ‘freedom’ and ‘state’s rights’ and anyway the South totally would have ended slavery on its own, so shut up!