Can you really separate the civil war from slavery? Really? What facts must you ignore to do that? What mindset must you have to do that? Ideological absurdity indeed.
People have a right to secede for any reason: To form a communist state, to form a theocracy, to form a monarchy. Yes, even to be slavers, which is just another (more honest) form of the governments I just mentioned.
They can form any kind of ugly, repulsive tyranny they want. Chances are that it will filled with oppression, just like 1000s of civilizations throughout human history. But that's neither here nor there. It is self-governance in action; not the U.S. government's place to intervene anymore.
I posted about this wa-aay earlier in this thread so you can't just say I'm "ignoring slavery."