The Emancipation Proclamation was issued in 1862, not 1864, and as Ed has pointed out above, it didn't really abolish anything.
And I think it's somewhat melodramatic to put the Reserve Clause in the same category as slavery. Ballplayers bound by the Reserve Clause at least had the option of retiring and doing something else for a living.
"Look at it, man", he said as if he had read my thoughts. "they call it America, and they call it civilization, and they call it television, and they believe in it and salute it and sing songs to it and eat and sleep and die still believing in it, and---and---I don't know", he said, taking another drag, "then some time the Mets come along and win the World Series___" Gram Parsons, quoted by Stanley Booth in Dance With The Devil