If one is taking the ultimate step of armed rebellion it stands to reason that by then the gloves would be off and the causes for the rebellion would be clearly stated. And nowhere in the documents of the time is any reason for secession stated more clearly and more forcefully than defense of the institution of slavery. But there were some discussion on tariffs. Alexander Stephens, for example, spoke on tariffs in December 1860.
"Yes, and Massachusetts, with unanimity, voted with the South to lessen them (tariff rates), and they were made just as low as Southern men asked them to be, and those are the rates they are now at."