The emanicpation proclamation in 1865 only "freed" slaves in the rebel states, not the slaves in the loyal slave states. This is indicative of the author's looseness with the facts and selective use of those facts which suit his agenda.
But it is educational to compare this article, and our view of the civil war in general, with the current war in Iraq. In both wars, it was necessary to create a coalition of support by giving different people in the coalition different reasons to join and support the coalition.
The original members of both coalitions are the ABOLITIONISTS.... those true believer Republicans who see slavery, and the Sadam-Baathist regime as evil. For them the war is a moral crusade to make the world a better place and to bring freedom to people who lack freedom.
But the abolitionists alone are not enough to make it happen. So the abolitionists expand the reasons for the war to include preserving the union and preempting a WMD first strike and enforcing UN resolutions and many other rationale that bring in enough supporters to make it happen.
But compare this: In the civil war, the first wave of Northern fighters were abolitionist motivated volunteers. But they died in huge numbers, leaving few additional abolitionists available to volunteer for the fight. Thus the draft was begun.
In the South, the death toll was also high. But they were defending themselves from the war of Northern aggression and could call on more volunteers with that rationale and not just on defending slavery.
In Iraq, the death toll on both sides is miniscule compared to our Civil War. Unlike Southerners, relatively few Iraqis opposed the influx of troops from outside their area. In fact, it would appear that most Iraqis welcomed the alleged liberators and the freedom that they brought.
Despite that difference between the two wars, another similarity exists in that the "freedom fighters" in both wars are plagued by small highly motivated bands of guerilla fighters or swamp foxes or whatever you want to call them. After the civil war, those fighters who just like to fight... it was their culture... fled West where they either seldom saw others with whom to fight and thus avoided fights, or became transients always looking for a fight.
FYI: the Emancipation Proclamation was issued on Jan. 1, 1863. Slavery officially ended with the ratification of the 13th Amendment in December of 1865. Hence, it is correct to point out that slavery existed under the U.S. flag from 1776-1865.
Wild overstatement. Contrary to the "John Brown" stereotype, a significant percentage of Abolitionists were also Pacifists who did not believe in war for any reason. (See the Quakers and the Seventh Day Adventists) Overall, there simply were not all that many Abolitionists. Their prominence, as mostly people of education and means who served as officers, and later wrote about their experiences is far out of proportion with their actual numbers. If you took all of the "Abolitionists" of military age in 1861, you would have been hard pressed to field a single division.
The Abolitionists, as a whole, did not especially care about the preservation of the "Union" either. They considered the Union with slavery to be an abomination and at least with the departure of the Southern states, they were free of slavery in "their" nation. They had little or no fondness for Lincoln and his willingness to tolerate slavery where it existed.
Contrary to what you wrote, the first waves of volunteers, both North & South were motivated by patriotism and "adventure". On the Northern side, it is impossible to overstate the outrage of people over the firing on the flag at Sumter. Ending slavery was not on the scope in 1861. People were slow to come to the conclusion that slavery had to end in order to preserve the Union.
As to the "draft", it was first instituted by the Confederate side. The Union draft impacted some states far more than others. Some states were able to reach their quotas without resorting to the draft at all and the so-called New York Draft Riots aside, even in states that conducted draft lotteries, the impact was minimal, especially after enlistment was opened for Blacks. The Confederate draft had a far greater impact across the South, especially in states where support for secession was tepid, at best. And even more than the draft, was the forced extension of enlistments for the "duration" by the CSA Congress which occurred early in the war. The Union side never extended enlistments yet did manage to have a high rate of reenlistment's even during the bloodiest years of the war. Some military historians credit the voluntarily mass reenlistment of those battle hardened Union veterans in 1864 with allowing for the successful ending of the war the following year.
Overall, there were a far higher percentage of "reluctant soldiers" on the Confederate side than on the Union side.