That's right. But slavery was no longer profitable in the North, so they wanted to end it. And they wanted to end it with no solution regarding the replacement of that number.
Had cooler heads prevailed, the institution of slavery would've ended. With the preaching of the Wesleys (late 1700s) and their followers, it would have ended much as it had in Britain. But slowly. And there wouldn't have been an entire race/class of uneducated and ill-prepared people simply turned out to fend for themselves.
Is that what they taught you growing up? What nonsense!
First, the heads were awfully cool until the anti-slavery movement seriously got going in 1830. Before then the debate was pretty rational for the times and the subject and almost NOTHING HAPPENED. Slavery was not dying out or even weakening, as it had decades earlier in England. Your precious Wesleys did not eliminate slavery and it was NOT about to die out. The US did not follow the English lead because there were too many slaves, too financially important, too close to home for Southerners to give them up.
On the eve of the Civil War, the value of slaves in the South was larger than the value of land. They were incredibly valuable and the South wouldn't give them up without a fight.
If Lincoln had allowed the South to secede, a country FOUNDED on the preservation of slavery would have continued slavery for a LONG, LONG time. We will never know, but probably not until the mid-20th century would slavery have ended in the South, though it all depends on how seriously the Confederacy wanted to join the community of decent nations.
Slavery didn't exist in Britain, it existed in the colonies, primarily in the Caribbean. And even though it was a compensated emancipation it was still done in the face of strenuous opposition from the slave owners.
And there wouldn't have been an entire race/class of uneducated and ill-prepared people simply turned out to fend for themselves.
And what makes you say that? Do you really think that slave owners would, at their own expense and in the face of a declining value of their asset, have footed the bill to educate and train their slaves for life after slavery? Slavery ending of it's own accord in an independent south wouldn't have left the freed slaves any better off.