Lincoln never said that secession was lawful.
What he said was:
The extent of our teritory in that region depended, not on any treaty-fixed boundary (for no treaty had attempted it) but on revolution 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. This is a most valuable,-- most sacred right--a right, which we hope and believe, is to liberate the world. 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 teritory as they inhabit. More than this, a majority of any portion of such people may revolutionize, putting down a minority, intermingled with, or near about them, who may oppose their movement. Such minority, was precisely the case, of the tories of our own revolution. It is a quality of revolutions not to go by old lines, or old laws; but to break up both, and make new ones. As to the country now in question, we bought it of France in 18O3, and sold it to Spain in 1819, according to the President's statements. After this, all Mexico, including Texas, revolutionized against Spain; and still later, Texas revolutionized against Mexico. In my view, just so far as she carried her revolution, by obtaining the actual, willing or unwilling, submission of the people, so far, the country was hers, and no farther. Now sir, for the purpose of obtaining the very best evidence, as to whether Texas had actually carried her revolution, to the place where the hostilities of the present war commenced, let the President answer the interrogatories, I proposed, as before mentioned, or some other similar onesYou have a right of Revolution. If you succeed in "obtaining the actual, willing or unwilling, submission of the people," then you, too, can not "go by old lines, or old laws; but to break up both, and make new ones."
Tell me, did Nat Turner's slaves have the Constitutional right to rise up against their masters?
Insurrection is not secession. Secession is neither insurrection nor rebellion.
Get with it.
You guys just want what you want -- to burn the South (or the West, or whatever) and take what you want. You just want it all your way, no arguments.
Your idea of a national motto is,
WE don' need no steenkin' bazzhes!!
You're all so charming. Why would anyone want to secede from you?
</sarc>