You really do need to study more.
Slavery was the flashpoint and no one denies that, but the crucial issue was states rights. As SATX mentioned, southerners felt that the federal government was overstepping its bounds and feared this could spread to other matters.
75% of those fighting for the South did not own slaves. Stonewall and Lee opposed slavery. The South had an abolitionist general. Why would these people fight a war if it was only about slavery? Answer - they would not. It would be foolish to believe otherwise. SATX is accurate.
You really do not understand how the "union" was viewed in that day and time. And you have lots of company. Nor the important of states autonomy, within the (then) limited bounds of the Constitution. Why were the Federalist papers written as such length and with such effort? To convince states to give up full autonomy to form the United States. This formation was very much in doubt.
Lincoln's saber rattling precipitated the war. As Lee stated, he never thought he would see the day that the President would raise an army to invade his own country.
And if you want to be honest, the Democratic party that you mention is in reality the Republican party today. The conservative southern Democrats left the Democratic party for the Republican party years ago.
Only 6% of southerners owned slaves
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