Critic answers Lincoln.
Lincoln used the word “irrevocable” in his first inaugural address. Below I re-post Lincoln's comment so you can read it for yourself.
“I understand a proposed amendment to the Constitution — which amendment, however, I have not seen — has passed Congress, to the effect that the Federal Government shall never interfere with the domestic institutions of the States, including that of persons held to service. To avoid misconstruction of what I have said, I depart from my purpose not to speak of particular amendments so far as to say that, holding such a provision to now be implied constitutional law, I have no objection to its being made express and irrevocable.”
You twist that to say "slavery was irrevocable".