Lincoln, along with a great many men who opposed slavery but were leery of the consequences of freedmen living side by side with white men, had been in favor of "colonization" for a very long time indeed.
It was kind of a fantasy of anti-slavery but not abolitionist men, since the logistics of the project made it utterly impractical. Doing so with today's tech and financial resources would be quite difficult, much less those of 1860.
Please don't imply that Lincoln was ever in favor of forcible deportation of black people. None of his discussion of colonization even hinted at it being anything but voluntary, and the idea was dropped once it became clear that there would be few if any volunteers.
I agree that it was impracticable. But it is also true that Lincoln, like other Free Soilers didn’t believe that whites and blacks could live in social equality. BTW, let me emphasize that I am not saying that that view was unique to Lincoln. Lincoln was never in favor of slavery, but it had nothing to do with his decision to invade the South.