Their right to be independent from what they regarded as a biased and despotic government in Washington D.C. (Same as today.)
Why did Confederates provoke, start & declare war on the United States?
When did you stop beating your wife?
When someone asks you to leave their home, they are entirely within their rights to do so. If you insist on staying when it has been made very clear to you that you are not welcome, you don't get to call them the aggressor when they toss you out of their home.
When you come back to their home with a big crowd of rowdies to whip their @$$ for tossing you out, you are still the aggressor.
But the fact is there was no "despotism" in Washington, DC, none, certainly from the Southern perspective because the South had always run things there.
The only new element was the November 6, 1860 election of the first ever "Black Republican" President, "Ape" Lincoln.
But nothing had changed, Lincoln was still in Springfield Illinois when Deep South Congressmen & Senators started walking out of Congress.
DiogenesLamp: "If you insist on staying when it has been made very clear to you that you are not welcome, you don't get to call them the aggressor when they toss you out of their home."
Forts Jefferson, Pickens & Sumter, were all Union property with Union garisons on November 5, 1860.
They remained Union property regardless of how many Confederates with cannons surrounded them, or what demands Confederates made.
DiogenesLamp: "When you come back to their home with a big crowd of rowdies to whip their @$$ for tossing you out, you are still the aggressor."
Exactly.