To the contrary. The speech is transcribed in its entirity from beginning to end. The context is all there, as are the page numbers if you wish to independently verify it. You simply don't like what the speech says so you have to invent an excuse, such as the above, to dismiss it.
I did, and only part of the speech is there. The dialogue between Senator Clingman and Senator Simmons actually begins on page 1474 and Senator Clingman is not complaining about the tariff, he is disputing Senator Simmons' claim that the new tariff will yield over $100 million in annual revenue. Senator Simmons maintains that since so little of the tariff is collected in southern ports that his estimates are correct. Senator Clingman says that the senator from Rhode Island is overlooking imports landed in Northern ports and destined to be shipped south, which he puts at $150 million per year. Since Senator Clingman provides no support for his claim it's impossible to take them seriously, any more than you can accept Senator Simmons' estimates. Regardless Senator Clingman is not threatening secession over the tariff, he is not saying that secession was the reason why seven states seceded, he is merely questioning the revenue estimates of Senator Simmons. Like I said, the whole thing taken totally out of context.