That conundrum was not resolved through speech, but through war. And, unfortunately, that war did not go far enough, as slaveowner politics quickly reasserted themselves.
Most of us would find a law that prohibits encouraging slaves from revolting or freeing themselves; to be horrid. Arguments that such laws don't really restrict freedom of speech because they're only encouraging an illegal act, would ring quite hollow. You might well be accused of sophistry if you made the argument seriously today; the act that's illegal to advocate is a fundamental right of all men, after all.
Conscripts are enslaved. What some may call a mutiny of conscripts others might call a slave rebellion. Let's just take that axiomatically for now. Obviously not all agree. But many accept that argument completely. Arguing it does not infringe free speech to call for people to free themselves, because it's only prohibiting the encouragement of a crime rings similarly hollow, from that perspective.
All true, but no one AFAIK was threatening abolitionists who used legal due process to actually pass the 13th amendment on free speech grounds. That activity is not the same as openly telling people to aid and abet breaking the current law, or conscientious objection.
> In the South abolitionism was illegal, and abolitionist publications, like The Liberator, could not be sent to Southern post offices. Amos Dresser, a white alumnus of Lane Theological Seminary, was publicly whipped in Nashville, Tennessee for possessing abolitionist publications.[57][58]
The southern states attempted to secede from the country, and fought a civil war that killed almost a million people to prevent the 13th amendment from passing.
The speech that advocates breaking the laws, but does not lead to immediate lawless action is already protected. I.e. if you say "hey you, I order you to take this gun and kill X!" then you're in trouble. But if you say something like "moral imperative declares that X should be killed" (and it's not a coded signal for an assassin but a genuine moralistic argument not intended to cause any specific action) then it's protected. That's why, for example, people marching through Oakland shouting "Death to America" were doing it in complete accordance with the law.
> What if I urge people, in a riveting call to action speech, to kill X celebrity or Y ethnic group?
I think the former is specific enough to be legally problematic, but I was actually under the impression that the second one is technically legal? (morally awful, but legally unprosecutable)
That's a grey area. The prosecution would need to prove that you intended for someone to commit the murder, that you advocated its imminent commission (or at least the imminent initiation of steps toward the crime), and that you believed your advocacy of such crime was likely to lead to someone carrying it out.
Such speech would only place you in legal jeopardy if it contains a direct and credible incitement to violence. If you simply said something like, "Let's kill all the Elbonians!” and nothing more then it would still be considered protected speech under current US Supreme Court precedents.
