This speech doesn't even come close to suggesting that the the "tariff" (actually an import duty) played any significant role in secession or the Civil War. As the speaker admits, the South was buying most of their European goods from Northern importers, so it was Northerners who were paying the vast majority of the import duties, not Southerners, and the speaker's assumption that the Southerners could simply shift their importing to Southern ports is highly suspect, since it is apparent that importing European goods through Northeastern ports was much more cost efficient.
Moreover, even if you assume that the speaker's numbers are correct that Southerners were buying $220 million worth of imports annually and thereby indirectly paying as much as $30 million annually in import duties, that would still be a mere pittance in comparison to the Republican threat to slaveholding (on which "peculiar institution" the secessionists placed a value of $3 billion).
Would your assertion still be true if the seceded Southern states charged a much lower tariff than the Northern states? That was the prospect facing the North.
As to your contention that the tariff played no role, consider the following newspaper editorials from early April 1861:
The New York Evening Post: "Bad as the law is in itself, the injustice of many of its provisions is hardly as gross as the stupidity of passing it at the very moment when the quarrel with the seceding states had reached its climax, and thus playing into their hands."
The New York Times: "How can we maintain any national spirit under such humiliation? We take the step of all others most calculated to alienate the border states and foreign nations."
The Daily Picayune (New Orleans): "Having driven the South to resistance, instead of adopting a policy of conciliation, it added to the existing exasperation by adopting a tariff as hostile as could be to Southern interests. The estrangement of North and South was not sufficiently marked and intense. New fuel must be added to the fires of strife, new incentives to embittered feelings."
Did you even read the speech? I am forced to conclude that you did not in light of such a comment. Either that, or you have difficulty with your comprehension skills. Allow me to assist you though with a key excerpt from the speech:
"One of two things must be done: either you must prevent imports into those States, which I do not think you can do; and I do not suppose there is a Senator on this floor who believes that, under the existing laws, the President has authority to do it; or you must call Congress together, and invest him with some authority. If you do not do that, you must establish a line of custom houses on the border. Is it not better for us to meet this question frankly on its merits? My apprehension, as I have already expressed it, is that the Administration intend, (I hope I may be deceived) as soon as they can collect the force to have a war, to begin; and then call Congress suddenly together, and say, "The honor of the country is concerned; the flag is insulted. You must come up and vote men and money." That is, I suppose, to be its policy; not to call Congress together just now. There are two reasons, perhaps, for that. In the first place, it would be like a note of alarm down south; and, in the next place, if you call Congress together, and deliberately submit it to them whether they will go to war with the confederate States or not, I do not believe they would agree to do it. Of course, I do not know what is the temper of gentlemen on the other side; but, though they will have a large majority in the next Congress, I take it for granted from what little I have heard, that it will be difficult to get a bill through Congress for the war before the war begins; but it is a different thing after fighting begins at the forts."
As the speaker admits, the South was buying most of their European goods from Northern importers, so it was Northerners who were paying the vast majority of the import duties, not Southerners
You have just demonstrated your comprehension of market concepts falls short of even your reading ability. Tariffs are not paid by one intermediary in the economy then forgotten about. They are passed on to the consumer by way of the prices.
and the speaker's assumption that the Southerners could simply shift their importing to Southern ports is highly suspect, since it is apparent that importing European goods through Northeastern ports was much more cost efficient.
It is not suspect in the least. If a barrier to trade exists in the north (i.e. a high tariff) but not in the south, the goods will go to the place where they can achieve entry, meaning the south. It's a simple matter of economic law, and also one that the otherwise economically incompetant yankees even understood. The New York Times even urged war on these grounds, noting that their high tariff would drive away trade, and the south's low tariff would pick it up. The New York Herald noted the same to be true. And sure enough, the Morrill bill virtually killed off trade with Europe after it was enacted.
Moreover, even if you assume that the speaker's numbers are correct that Southerners were buying $220 million worth of imports annually and thereby indirectly paying as much as $30 million annually in import duties, that would still be a mere pittance in comparison to the Republican threat to slaveholding
Not when you consider that those figures were from the 1857 tariff, which was low and favorable to free trade. The grievance was with the Morrill act, which practically destroyed international trade with Europe. The southern economy was almost entirely export-based, and when trade halts so do exports.