> how do you get out of the proposition that someone has to decide
I agree ultimately some subset of people would need to decide. My question is who?
How is that working out in the People's Republic of China? They have a very concrete definition of what dangerous speech and have legions of people to decide whether individual instances are dangerous and to remove them.
Clearly, their system illustrates the hazard of your viewpoint.
And I suspect that if you polled in China, you'd find a majority agree with the regulations on speech, and sincerely so (not saying yes out of fear). Meanwhile, things are much freer than they were. I'm currently reading a Chinese novel, The Three Body Problem, set partly in the Cultural Revolution, and it pulls no punches about how awful it was.
Of course you would, polls like all speech are tightly controlled.
And those who deliberately inspire violent behavior with their speech are very, very careful to make sure it's not an explicit call to action. This is not new. "Will no one rid me of this meddlesome priest?" has been around for a long time.
Are you proposing that nobody can decide what speech is dangerous?
Are you suggesting there is no such thing as dangerous speech?
Are you suggesting that having someone decide what speech is dangerous is actually worse than the dangerous speech itself?
If you're not suggesting any of these things, then how do you get out of the proposition that someone has decide?