I didn't get that impression from the article at all. That must be your own subjectivity giving you that result.
In 1776 when all the states in the Union were slave states, the abolition of slavery in each state was gradual. It picked up over the years, and the process was inevitably in the direction of abolition. I used to know where a GIF map was that showed the effect.
The point is, had everyone just left it alone, the effect would have eventually reached all the states, and it would have been eliminated peacefully.
And with the oncoming Industrial Revolution and modernization in general, the war was unneeded and catastrophic. Shelby Foote, who is probably one of the most prolific and objective scholars/writers on the subject, is quoted:
"Right now I'm thinking a good deal about emancipation. One of our sins was slavery, another was emancipation. It's a paradox. In theory, emancipation was one of the glories of our democracy - and it was. But the way it was done led to tragedy, turning four million people loose with no jobs or trades or learning. And then in 1877 for a few electoral votes, just abandoning them entirely. A huge amount of pain and trouble resulted. Everybody in America is still paying for it.”
Slave rebellions were a serious fear in the South. Many believe that the fear of reprisals is what convinced slave owners to stand firm and demand that the US Constitution allow slavery back in 1789. In fact, the year after it was ratified (1792) all the slaves in Haiti rebelled, tortured, and killed everyone who was white or even 1/8 white. There had been several smaller attempts at slave rebellion in the South as well. Given the choice to keep slavery or to risk being butchered in retaliation, most powerful people in the South chose to keep slavery. John Brown’s raid shocked the people in the North, but in the South, it spread terror.
Read the paragraph above. It explicitly states that the South insisted on maintaining slavery as a choice between keeping slaves or risking being butchered in retaliation and that the South insisted that the new Constitution allow slavery because of fear of rebellion. How else should this paragraph be interpreted other than as an argument that the South maintained slavery mainly because of fear of reprisals. This is demonstrably false. If the South wanted to, they could have sold their slaves to owners of sugar plantations in the Carribean or just sent them back to Africa. They did not do so because they weren’t keeping slaves because they feared reprisal, but because their economy and social structure relied on slavery.