There is no doubt that tariffs benefitted the North economically at the expense of the South. This was a significant irritant to the South. I am reminded of a statement I found in the New Orleans Picayune newspaper quoting the Daily Chicago Times newspaper on/of December 10, 1860 that admitted:
The South has furnished near three-fourths of the entire exports of the country. Last year she furnished seventy-two percent of the whole . . . We have a tariff that protects our manufacturers from thirty to fifty percent, and enables us to consume large quantities of Southern cotton, and to compete in our whole home market with the skilled labor of Europe. This operates to compel the South to pay an indirect bounty to our skilled labor, of millions annually.
No doubt some Southern politicians realized that the two new tariffs (Morrill vs. Confederate) with their different tariff rates would result in some big future advantages to Southern ports and businesses. Northern newspapers in early 1861 recognized the harmful effect of the two tariffs on Northern ports and businesses.
As you said, tariffs weren’t the prime motivators of the secession of the South. However, the potential loss of revenue to the Northern government caused by the two different tariffs was, in my opinion, the main reason Lincoln provoked war with the South. Face it, he intentionally did just that and did not want compromise with the South. With war, Lincoln could blockade the Southern ports and starve the Southern government of import revenue and needed supplies.
The US government was virtually broke when Lincoln became president due to previous high government spending and current plans for even more spending, such as the Northern railroad route to the West coast. The US government very much needed more revenue. If memory serves, even Congress was not getting paid because the Treasury was nearly empty.
“…that ‘my fellow citizens understand the true principles of government and liberty [and appreciate] their inseparable union.”
- George Washington
“I can scarcely contemplate a more incalculable evil than the breaking of the union into two or more parts.”
- Thomas Jefferson
“ The right of a state to secede from the Union, is equally disowned by the principles of the Declaration of Independence.”
- John Quincy Adams.
“Secession, like any other revolutionary act, may be morally justified by the extremity of oppression; but to call it a constitutional right, is confounding the meaning of terms, and can only be done through gross error, or to deceive those who are willing to assert a right, but would pause before they made a revolution, or incur the penalties consequent upon a failure.“
“…disunion by armed force is treason.”
-Andrew Jackson
In February 1850, he (Zachary Taylor) held a conference with southern leaders who had threatened secession. Taylor told them that, if necessary to enforce the laws, he would personally lead the army. Persons “taken in rebellion against the Union, he would hang . . . with less reluctance than he had hanged deserters and spies in Mexico.”
Millard Fillmore sent government troops to the South to act against rumors of secession by South Carolina.
“ And this brings me to observe that the election of any one of our fellow-citizens to the office of President does not of itself afford just cause for dissolving the Union.”
- James Buchanan
I guess Lincoln wasn’t the only one after that revenue.