Correct me if I'm wrong, but wasn't this a popular opinion among a lot of abolitionist too? There was a general feeling that white people could never get over their racism so the only way for the black community to thrive was to send them somewhere away from whites where they could form their own nation. I think the whole "forty acres and a mule" thing came from General Sherman having a conversation with a black pastor who had become the de-facto leader of a small army worth of runaway slaves and asking him if his community would prefer living among the whites or being given a region of land to form their own community and apparently the chose the latter.

This isn't me defending Lincoln, dude was no abolitionist, but more trying to understand the historical context in which that opinion of him formed.