Those two aren't mutually exclusive, and I didn't gather that they were from DiLorenzo's article. Lincoln was a high-tariff man and the tariff issue in the 1860 election was calculated to play well in the more populous north.
Of course Lincoln addressed himself to those in the manufacturing community who desired protection, though it had little influence on the stance he took in the election. Agree or disagree, approve or disapprove, that is a prerogative of any politician or elected official, as President Bush could tell you. Protective tariffs may not be the best of policies, but representative politics means speaking to the concerns of citizens. How was support for the tariff more reprehensible than addressing oneself to slaveowners and attending to their interests?
Concentrating on the tariff issue and throwing away the other issues of 1860 allows one to portray Lincoln and the Republicans in the cynical terms of power politics and economic interests while depicting Southerners and secessionists in the familiar hazy light of victimhood and martyrology. When we look at all the issues of that year, we see that no one was far from political or power considerations, least of all the fireeaters and secessionists. Examining that fuller picture we see that Lincoln was not devoid of principled concerns either.
Indeed, an examination of other political actors of the era could tell us much. It would give us an understanding of how political and economic ideas, as well as philosophical or moral concerns, shaped the actions of all political actors and movements. Perhaps we would also understand finally that the Morill tariff was a result of proto-secessionist politics and secession, and not their cause. The Southern-oriented Democrats had been the majority party since Jackson, or even Jefferson. Given the rules of the Senate, they could have blocked any increase in the tariff, if they had remained together as a party and really cared about the tariff more than about slavery.
One reason why these threads are so circular and get nowhere is that people begin start with the dismissive assumption that we learned in school that it was "all about slavery" and end with the conclusion "you see, it wasn't all about slavery." I didn't learn in high school that it was "all about slavery" and I doubt most people did either, especially in the South. I don't know what kids are learning now, but Di Lorenzo is actually more simplified and less nuanced than the average high school textbook of previous decades.
Why not begin with the new orthodoxy of Di Lorenzo and start moving in the direction of "you see, it wasn't just about tariffs?" How far will you get?