I didn’t spout off on you. I said you were correct.
Since you started, no southerner can ever honestly answer the question: A state’s right to do what exactly?
Their Declarations of Secession answers that question. Slavery
But also to control their own ports and set their own tariffs so as not be exploited by Northern industrialists in the same fashion that British mercantilists once exploited the colonies. Also to enjoy benefits of their own wealth - at they time seceded the South was paying about 70% of Federal revenues, with less than half the representation. Sort of a "taxation without representation" situation. I can think of worse reasons to secede.