Indeed. All you have to do is look up and read the resolutions of secession passed by the Confederate states - all of them say it is about slavery and the supremacy of the white race. The stump speeches from the Confederate politicians at the time likewise - the Cornerstone Speech from the Confederate Vice President is perhaps the most illustrative. Look at the editorials in the newspapers in the South at the time. Look at the debate among the Confederate generals as to whether or not they should use black soldiers would undermine the very cause they were fighting for. It is irrefutable and overwhelming. Yet, when you point these facts out, the responses you normally get are "screw you" (or the equivalent)...nothing substantive - or they find some quotes of Lincoln where he was playing politics to placate the handful of slave states that did not secede (and he did not want to spark further secessions) as somehow explaining away all of the above.
It is also true that after the war there were northern politicians who decided to take advantage of the South's weakness and basically ravaged them, but that doesn't change the facts above. The current narrative that it wasn't about slavery but about "states rights" is actually not a new narrative - it began right after the war ended by the Southern politicians working to save face after their defeat - so the proceeded to rewrite the history of why the war began and that has taken root since that time among many...and the behavior of the northern politicians to ravage the South in the aftermath of the war added fuel to the fire of that narrative - they saw the "northern aggression" that was being described as the cause for the war in the rewriting of history...so it is completely understandable how this would be believed.
I would like to see an interview of Corey Stewart wherein these documents are presented to him to review and get his reaction as to his opinion after reviewing them and see what he has to say, but unfortunately the only kind of interview you could get would be someone screeching at him calling him a racist.
Four of them say something along those lines. What about the other 7 states? Do we let 4 speak for all 11?
People trot that out because it fits the narrative they want to push. The truth is that the war was in Lincoln's hands, and it doesn't matter why the various states seceded. Probably every single Northern state would agree with every bit of that racist crap during that era in history.
You want to pretend they don't, but you should look at the Illinois "Black codes" sometime if you want to know what Lincoln's home state thought of blacks.
The war was fought because Lincoln wanted it fought. He sent a war fleet to fire on the confederates at Sumter to start the war. He was going to start it one way or the other, because he needed the war. Nobody in the South wanted it or needed it, but Lincoln did.