Comment 54 in the thread said 75% of the tariffs were paid by the south. Without trying to confirm it, I assumed that was correct.
The quote you provided, talking about what the situation HAD been over the previous 70 years, ignores that the times had changed from the beginning of that time to the end. From 1844 to 1860, seven states were added to the union. MI, WI, MN, FL, TX, CA, and OR. Areas of the country where slavery was considered vital to the economy had reached it's natural limits, while the remainder of the country continued to expand. I believe that politics forced compromises in the 20 years prior to the war to appease the south, with the intention of holding the union together, but the trend pointed to an inevitable conclusion.
And yet upwards of 95% of all tariff revenue was collected in Northern ports - specifically New York, Boston, and Philadelphia - as government documents for the year just prior to the rebellion show. How do you explain that? And if you do assume the South paid 75% of the tariff then what were they importing in such massive amounts?