His Meditation

[busker]

That, however, was not in the poem.  At most, it might have made thoughtful readers ponder Lincoln's problem - I make no claims about that being its intent, it just lays out some thoughts about Lincoln's predicament and his reasons for it.  Perhaps it could be more visual - he picks up a pen, dips it in black India ink, and writes a note to himself about the proposed colony on San Salvador, or his Navy's troubles with "contrabands" in the Sea Islands.  Does that sound like something that might pass muster, if well done?

The question remains - what is the poem trying to do?
If it's just telling the facts, then why do you need a poem? A wikipedia entry would do the job better.

If it's explaining or putting forward a point of view, a message, what is that message? 

If it's that 'in the end, Lincoln too didn't want to live alongside blacks as equals, and therein lies the irony', then the 'great heart' etc undercuts that message. It's confusing. Sure, he had a great heart (did he? it was other men and their children who were dying, not him...but that's another story) compared to, say, Leopold II, but that's not saying much. 

If the message is that 'Lincoln was all right, but knew that his countrymen were utter and rabid bigots', then the lack of a value judgement on said countrymen is puzzling. It's like writing a  poem sans irony humanising the commanders of Belzec, Sobibor, Maidanek, Chelmno, Mauthausen, Belsen, and Treblinka.

They looked and talked and walked and quacked like humans, we don't need further reassurance about that, so what's the point?