he definitely wanted to free the slaves, talked about it and wrote about it extensively, and definitely why we they started the civil war.
his bff was a former slave, even... and just how do you suppose he was supposed to add that 21st amendment before the civil war? you know the president isn't dictator, right? half of congress was the south, at the time... and they were voting pretty heavily in favor of slavery...
members of congress actually beat members of congress to death, in congress, in the lead up to the civil war... while arguing about slavery (in particular about accusations of members of congress owning slaves for raping purposes, rather than their arguments about labor)