As always, you misunderstand Lincoln.
What he actually said was:
Lincoln believed that such an amendment at that time would merely make express what the Constitution then implied.
DeoVindiceSicSemperTyrannis: "The South didn't pay any heed to this, which shows that there were other issues going on between the two sections besides slavery."
In fact, for over four months -- from November 1860 to March 1861 -- many "compromise" proposals were forwarded in Congress and among various states, all with the thought of enticing Deep South secessionists back into the Union.
None -- zero, zip, nada -- had any effect or received any positive response from Confederates.
So the fact is that nothing was going to change their course at that time.
However, on the question of what drove Deep South Fire Eaters to declare their secession in the first place, they themselves were 100% clear on the subject, at the time.
It was to protect their "peculiar institution" slavery against abolitionist "Ape" Lincoln and his Black Republicans, pure and simple.
Only long after the fact did they begin to suspect other reasons might also be convenient to put out, and so they started concocting cockamamie nonsense for distribution to gullible useful idiots like our own DiogenesLamp DL, & others.
Nonsense like: "New Yorkers were stealing Southern wealth."
The real fact is that nearly 80% of Southern cotton shipped directly from Gulf Coast ports to their European customers, not through New York as DL pretends.
That's one reason why the economic Panic of 1857 affected Southerners less than other regions.
They were not as tied into the New York financial world as others were, and didn't suffer when it collapsed in 1857.
So, yet another piece of DL's Lost Causer mythology bites the dust.
Does DL care? Naw, he's a devoted propagandist and facts don't matter to him in the least.
You are the master of the irrelevant. All that cotton was shipped on New York controlled ships and under New York controlled contracts.