Gee, when I took AP American History, we read the Georgia Ordinance of Secession, which begins: "The people of Georgia having dissolved their political connection with the Government of the United States of America, present to their confederates and the world the causes which have led to the separation. For the last ten years we have had numerous and serious causes of complaint against our non-slave-holding confederate States with reference to the subject of African slavery. They have endeavored to weaken our security, to disturb our domestic peace and tranquility, and persistently refused to comply with their express constitutional obligations to us in reference to that property...
Nothing about taxes. The whole thing is about "that property".
Now, I am more sympathetic than many to the enormous difficulties which arose for our Southern brethren out of their cohabitation with a large and generally hostile population of African-descended persons. Certainly we in the North, in the methods we chose to ameliorate the difficulty of living with a much smaller population of African-descended persons did not distinguish ourselves.
I think the Great Emancipator, or Great Constitution Destroyer (as you will), said it best: "One-eighth of the whole population were colored slaves, not distributed generally over the Union, but localized in the southern part of it. These slaves constituted a peculiar and powerful interest. All knew that this interest was somehow the cause of the war. To strengthen, perpetuate, and extend this interest was the object for which the insurgents would rend the Union even by war..."
"That property" was the problem. Of that, there can be no doubt.
Why did so many non slave owning, and most likely never to be able to own a slave, Southerns fight? Why did so many southern white laborers, in many ways their labor value suppressed by slave labor, why did they support and fight for their state?