This is exactly on target. The left's agenda then was turning a war that was dedicated to preserving the union into a war dedicated to radical abolition and reconstruction. Their talking points became the mainstream talking points a little over a century later. After all, what do little kids learn about the Civil War in elementary and middle school history classes? Do they hear how Lincoln, Grant, and Sherman were heroes who saved the union? No, they're heroes for "freeing the slaves"!
History is what folks say it is
Unfortunately
We would all benefit from a more comprehensive understanding of that era today