We could just make speech that directly glorifies or encourages violence illegal. Basically just an extension of laws against violent threats or speech that does direct harm.
It would be much harder to abuse such a restriction on speech, and it would cover all violent or genocidal movements without singling out a specific ideology.
One of the best ways around the first amendment is to throw away any notion of offensiveness or obscenity, and focus on victims. You can’t fraudulently shout “Fire!” in a crowded theatre because the people who get injured in the panic will be victims. You can’t possess child porn because minors have no right to grant sexual consent and the existence of such media further victimizes them. You can’t distribute private porn made with your partner without their permission for similar reasons: because your partner didn’t consent to it, and would be victimized by its distribution. You cannot threaten to assault or kill someone, or call for others to assault or kill someone, because it amounts to conspiracy to commit a violent crime.
None of these restrictions on speech focus on the speech being offensive, they focus on the speech having direct harmful consequences to others. It draws the line of where your rights end at where others’ rights begin.
I don’t see why we can’t extend this to cover inherently violent ideologies like Nazism, where glorification of it, by definition, is a call for violence against specific members of our society. If you celebrate the Holocaust and demand similar action today, the victims are the people who you are asking the state to murder. There’s no reason to tolerate that as free speech, because the people being targeted have the right not to be murdered. If it’s illegal to call for the murder of 1 person, why not make it illegal to call for the murder of millions of people?
