So you're in agreement with the author, then.
No.
Very few Northerners cared about slavery one way or the other in the South.
Abolitionists in those days were a fringe group equivalent to today's, oh, say, Libertarians -- meaning important, but a small minority.
Indeed, nearly all Northerners cared more about Union than about slavery, and that is why before 1856, they all voted for pro-slavery parties -- the Democrats and Whigs.
All Northerners were content to let slavery rule in the South, if that was the price of Union.
But what Northerners certainly did care about was slavery in the North and western territories: they didn't want it -- no way, no how, under no guise.
But the Supreme Court's 1857 Dred Scott decision effectively meant slavery was legalized everywhere, and at that point, the North fully switched from pro-slavery Democrats & Whigs to anti-slavery Republicans.
Of course, neither Lincoln nor most other Republicans wanted to abolish slavery in the South, they just wanted to be d*mn certain it stayed there.
Sorry, but you'll never understand the Civil War if you begin by thinking of the Slave Power as a "victim".
From the beginning, slave-holders were aggressors on the American body politic.