Heh.
As with all things of this nature, there is a kernel of truth.
Lincoln was a man of his times. And a politician. If you think that just because it was the 1860's and Lincoln, that politicians were different from today's crop, think again.
Yes, the Emancipation Proclamation was a political ploy. It was hoped Negroes would rise up and fight against the South.
Here's a fascinating article on Slavery in the North: The World as it was.