There’s quite a bit of fail in here about the origins and motives regarding the Civil War.
The war was fought for many reasons, the primary one being the preservation of the United States. President Lincoln stated as much on several occasions. There were certainly economic reasons as well, but from a morality standpoint, that doesn’t become much of an issue until about 1863. Do not forget: the North technically started the war itself, but the action that made war inevitable was the secession of the South.
Secession occurred because the Southern states did not feel the federal gov’t had the power to apply federal legislation to the territories, despite the fact that the federal gov’t had been doing that exact thing since before ratification (see: Justice McLean and Justice Curtis’ dissents in Scott v. Sandford). This was the view of those Southerners who supported Chief Justice Taney’s decision in Scott v. Sandford. There were others, of the Stephen Douglas ilk, who felt that state sovereignty as expressed through the doctrine of popular sovereignty was being undermined by federal legislation being applied to the territories. Either way, Southerners felt that the federal gov’t was unconstitutionally encroaching upon state sovereignty, hence the “states’ rights” argument.
This ignores the other half of the Southern argument, namely that states cannot even vote on their own to bar or accept slavery. These are the ones who were turned off by Douglas’ pitiful attempt at bridging the gap between these two factions in the South and elsewhere (the Freeport Doctrine).
Regardless, the entire argument from either Southern faction still boils down to the idea that blacks were 1) not fit to ever become citizens of the Unites States, 2) that slavery was the natural condition of blacks OR blacks were of such an inferior status that any association with whites, especially as slaves, would be of benefit to them.
The entire argument from the South really heavily leans on the idea that certain races can be construed to be property. The states’ rights argument is a more general presentation of a property rights argument. And what specific property are we talking about here? People, specifically those of African ancestry.
So to argue that the South seceded due to economic reasons largely ignores that upon which their economy was based. HOWEVER, even the economic argument is vapid and self-serving at best. The fact is that while the cotton industry obviously drove the Southern economy, slavery itself was not very economically efficient at all.
For the North, the war was less about slavery and more about preserving the United States. To the North, Southern secession was a direct threat to the sovereignty of the United States, in the form of insurrection and rebellion. In Article I.9.2 of the Constitution, it clearly states that Congress has the power to suspend the writ of habeas corpus in case of rebellion. In Article IV.4, it clearly states that the President can exercise Congress’ power to protect any and all states from insurrection or rebellion IF Congress is unable to convene. It’s hard for them to convene when 7 states have seceded and confiscated property belonging to the United States in the process. Finally, Article II.1.8, the Presidential oath is enumerated, in which the President is sworn to uphold the Constitution of the United States. The Constitution itself is a compact between states, as the South rightfully argued when protesting certain Northern states’ refusal to adhere to the Fugitive Slave Law. However, when the South seceded, they also violated this compact, and the Supremacy Clause of the Constitution, which all 7 states originally signed on for, clearly states that the Constitution, NOT the states themselves, are the ultimate sovereign. James Madison argues this point quite eloquently in Federalist #44.