Good for him! The time for negotiation is before the war, not after you've been utterly destroyed. For him to give in to the slave-owning south having won a civ

Good for him! The time for negotiation is before the war, not after you've been utterly destroyed. For him to give in to the slave-owning south having won a civil war at such high cost, would have been snatching defeat from the jaws of victory.