That's the propaganda we keep hearing, but in practical terms there was very little that Lincoln or the Republicans could actually do to interfere with their economic system. In real terms, the South would have seen massive increase in capital from getting out from under trade and taxation rules that benefited New York and Washington DC at their expense.
The powerful corruption cartel running things in the North would have lost huge amounts of money, and the Southern states would have gained huge amounts of money.
It was the underlying but unspoken reason why the North went to war.
“There was very little that Lincoln or the Republicans could actually do to interfere with their economic system.”
That is true. But did the Southerners believe that, did they really believe that Lincoln and the Republican administration would strictly follow the Constitution, Dred Scott Decision and their own rhetoric. Or did they view Republicans as lying rats, intent on destroying slavery, elevating the black man to equality with whites, misogamy, etc.
People act on what they believe to be true, where it true or not.