He favored leniency towards them, and the radicals who took over after he was gone wanted vengeance for his death, and wanted to punish the South to the maximum extent.
He likely would have held back some of their worst impulses.
The War of Northern Aggression.
Lincoln suspended habeus corpus.
He shit down newspapers for political position in violation of the First Amendment.
He began us on the course of an imperial federal government.
He pursued a war that killed over half a million American men.
Slavery would have died out - as it had in other countries - over time.
Africans were hardly the first peoples to be enslaved.
Had he not been killed would he have been remembered so fondly?
The Confederacy started the war