My ancestors were slave owners in Cuba. Slavery was a cancer in Cuba and it was a cancer in America.
It would have been much better if Southern Americans had picked their own cotton and Cubans had cut their own sugar cane. It would have been much better if we had not grown either cotton or sugar cane. The North's blessing was the fact that it had poor agricultural land that forced it into manufacturing as the road to wealth.
Slavery undermined free labor and created a perpetually embittered underclass that later contributed to a Communist Cuba and to blighted American inner cities. Over a century later, we are still paying the price.
That being said, it must be pointed out that neither Lincoln nor the North initially saw the Civil War as a war to end slavery. The initial war aim was to “preserve the Union”. Only later was the Civil War portrayed as a war to end slavery.
And I have never said that it was. What I have said is that it is was by far the single, most important reason why the south launched their rebellion.