I'd be glad for some data on this. Butler was a trial lawyer. Where did this expertise in shipping come from?
There is not, so far as I know, and 4CJ has not provided any after at least ten days -- there is no evidence that Lincoln asked Butler about transporting blacks at all, let alone with the aid of the US Navy, except this book of Buter's from 1892.
Butler is on the public record in 1865 as favoring black suffrage. It just seems totally at odds with a position to force them to leave.
Walt
I've seen Butler's Book offered for as low as $45 on the net. Just because you disagree with Butler's statements does not mean that it is not true.