You answered your own question - why would Butler make up such a quote? Lincoln had attempted in late 1864 to retain Commissioner of Emigration Rev. James Mitchell...
You are the one making things up.
Lincoln didn't attempt anything of the sort based on the record so far shown.
Mitchell wrote to President Lincoln in October, 1864. He said he had not been paid in 4 months and that his files had been removed "long before".
Lincoln apparently inquired whether Mitchell could be kept on as commissioner of emigration or another position found for him -- the perfect example of 19th century political patronage.
You won't make the record show anything else -- and you cannot quote Lincoln as favoring colonization in 1863, 1864 or 1865.
Walt
Butler quotes Lincoln, and it's documented that Lincoln summoned him to Washington in 1865.