I think rather that DL’s main argument is that the proposed Corwin Amendment proves the North was not anti-slavery. I have witnessed the evolution of his thoughts about the proposed Amendment. Firstly he came onto one of these threads proclaiming that Lincoln (by the proposed amendment) intended to make Slavery “express and irrevocable”! He was then shown that Lincoln meant that he saw no reason that the amendment shouldn’t be made express and irrevocable (not Slavery). Then he came up with (with zero proof) and pushed the idea on a thread here that Lincoln was involved in the writing of the amendment! Lincoln, upon bringing up the matter of the Corwin Amendment in his 1st inaugural, stated “which I have not seen”. But DL doesn’t, couldn’t believe Honest Abe’s own words. Instead he has to make them into pretend things that are more palatable to himself.
Everyone knows that Lincoln had already said to Greeley that if he could preserve the Union half slave, all slave or no slaves, he would do it. His primary objective was to preserve the Union! So there was nothing new in the proposed Amendment. Although DL seems to think there is.
Of course the “proposed” Corwin Amendment was only ever ratified by 5 States, two of which later rescinded their ratifications. One as recently as 2014. Buchanan actually signed it even though his signature wasn’t a requirement. So, not only is the “proposed” Amendment academic, it is a moot point. Despite DL handwringing it to death.
I have always and will always state the obvious history. The Southern states seceded to preserve the institution of slavery from the perceived threat, real or otherwise, of Northern abolitionists. The Northern states refused to recognize the right of secession, and fought to preserve the union. Over time this took on the added tenor of a crusade to end slavery.
All the rest is just chatter.