You do know that Abraham Lincoln supported the Corwin Amendment which would have made slavery permanent and irrevocable in the Union?
If you don't believe me, go read Lincoln's first inaugural address. Lincoln was willing to keep slavery. What he wasn't willing to do was to let the South trade freely with Europe outside of his economic control.
Lincoln did say in his first inaugural that he supported the Corwin Amendment. But you are very much mistaken when you say the Corwin Amendment "would have made slavery permanent and irrevocable". That is not at all what the Corwin Amendment was about. You should double check your internet source for that, or old newspaper, or whatever. That is now a common trope of the lost cause mythology. You must all have a common source of misinformation.