If you believe that rights are only decided by conquest, then you have effectively made the argument to justify slavery.
That is MOT what that means. It is a simple statement of fact. You cannot point to one portion of the US constitution that gives any faction the right to disunion.
Slavery was appalling then as it is now. The only treason there was a war over it here in the US is becsuse democrat, elite, plantation, slave owners wanted one. They wanted it so bad that they chose to secede because Lincoln was elected. Before his inauguration they had already begun their traitorous actions