I'm not informed enough to get into this history in detail, so I'll acknowledge that you may be right. However, my point is, war is incredibly destructive, and its impossible to foresee how it will work out. In my opinion, war is rarely worthwhile to prevent secession. Also, because the fight is often actually about access to resources, other reasons for the fight are routinely trumped up to justify preventing a region from seceding. For example, Lincoln used the Emancipation proclamation to motivate greater enthusiasm for the war.
"The Proclamation did not apply to the five slave states that were not in rebellion, nor to most regions already controlled by the Union army; emancipation there would come after separate state actions and/or the December 1865 ratification of the Thirteenth Amendment, which made slavery illegal everywhere in the U.S. The Proclamation did not compensate the owners, did not itself outlaw slavery, and did not make the ex-slaves (called freedmen) citizens. It made the eradication of slavery an explicit war goal, in addition to the goal of reuniting the Union.[1]
.....The Proclamation outraged white Southerners who envisioned a race war, angered some Northern Democrats, energized anti-slavery forces, and weakened forces in Europe that wanted to intervene to help the Confederacy....
Wikipedia