I agree with what you say to a point. The speech I posted, made in 1859 tells of another motive to abolish the present government and create one where slavery will not be a part of. After the decision of Chief Justice Taney, staing that the Missouri Compromise was unconsitutional because congress couldn't decide where slavery was legal. The Northern anti-slavery states threatened secession.

I also read that Lincoln said, and I'm paraphrasing here,

"secession is not legal, but neither can the government legally bring them back into the Union by force"