lincoln and secession

Lincoln did articulate a view of secession that would have been welcomed in 1776: "Any people anywhere, being inclined and having the power, have the right to rise up and shake off the existing government and form a new one that suits them better. ... Nor is this right confined to cases in which the whole people of an existing government may choose to exercise it. Any portion of such people that can may revolutionize and make their own of so much of the territory as they inhabit." But that was Lincoln's 1848 speech in the U.S. House of Representatives regarding the war with Mexico and the secession of Texas.
Why didn't Lincoln feel the same about Southern secession? Following the money might help with an answer. Throughout most of our history, the only sources of federal revenue were excise taxes and tariffs. During the 1850s, tariffs amounted to 90 percent of federal revenue. Southern ports paid 75 percent of tariffs in 1859. What "responsible" politician would let that much revenue go?