I think most here forget that the US Congress and Lincoln had stated that the war beginning was not about slavery, and as primary sources, do not in any way support the slavery argument.
That argument was used to inflame both before war and after.
It is important to take into consideration the people and words of the time.
3/18/1861 It took only a week for Northern newspapers to understand the meaning of the low Confederate Tariff announced the week earlier in Montgomery.
The Boston Transcript wrote,
"It does not require extraordinary sagacity to perceive that trade is perhaps the controlling motive operating to prevent the return of the seceding States to the Union.
"Alleged grievances in regard to slavery were originally the causes for the separation of the cotton States; but it is apparent that the people of the principal seceding states are now for commercial independence. They dream that the centers of traffic can be changed from Northern to Southern ports.
"The merchants of New Orleans, Charleston, and Savannah are possessed with the idea that New York, Boston, and Philadelphia may be shorn, in the future, of their mercantile greatness, by a revenue system verging upon free trade.
"If the Southern Confederation is allowed to carry out a policy by which only a nominal duty is laid upon imports, no doubt the business of the chief Northern cities will be seriously injured thereby."
Follow the money.
It would be folly to think that the Northern States did not recognize that abolition would have the same effect on cotton production as taking tractors from wheat farmers today would have on wheat production—which would adversely affect Treasury revenue as well. Without a crop, there would be nothing to tax.