I dare say that those in charge of the South, i.e., Southern Slave Power were not "lovers of liberty". They were the opposite. Stop kidding yourself that this was a situation of "secession and rebellion against tyranny". That is pure and unadulterated self delusion. This was a separation by the southern slave states, and only the southern slave states in order to maintain their tyranny over their slaves.
I posit ye this: would the Confedacy have allowed a non-slave State into their Confederacy? Would they have accepted a Northern State? I'll make it easy for you, the answer to both questions is, "no". The founding principle of the Confederacy was that the white man was superior to the black man. Their plan was take their Empire based on Slavery and spread it west, then south through Central America, then across the top of South America and thence onward to Cuba.
Like i stated previously, if you cannot acknowledge a state’s right to secede for any reason, then you have no rights beyond those granted by the government. Rights are not rights if they can be abolished by the government at the point of a gun. I understand that the Confederacy had not the moral high ground in slavery, but the right to secede did exist. If you could envision any reason for which you would separate yourself from a tyrannical government, and i can think of a few, secession might be your only lawful path. I am speaking in contemporary terms.