DC,  As Motley points out, Lincoln was constrained by reality (politics).  Regardless of what he believed he could move no faster than the nation was ready to accept change.  If Lincoln were alive today and asked about colonization my guess is he would have some amusing self-deprecating story about bad ideas and tell us that is all he could politically come-up with at the time that most whites would find acceptable.  You have to give the man credit for self-assessment and knowing limitations; when most black leaders of the day told him it was a bad idea and they wouldn't support it, he dropped it.  Blacks one that argument, stopped a bad idea, and changed the course of history all because of the man named Lincoln.  How many white men in power at that time would have even listened to those blacks let alone concede their plan/policy to them?