Why is speech a specific, precise red line? Yelling "fire" in a crowded theatre (and I'm aware that the case which coined this phrase was completely stupid, but the phrase itself stands) should probably not be legal, even though it is speech.
The line gets s lot blurrier when you call fo arson and someone acts on it and burns down a building. Should you be liable for the actions of the third party that burnt down the building? Imho there's some responsibility to be held, yes, despite you only calling for it.
But I wouldn't want anybody to wield the power to legally shut down other people. The amount of abuse that can generate in the wrong hands is Tremendous (see what I did there?)
Everyone here subconsciously understands that most laws are only intended to apply to people who regularly cause problems, and that creates an unjust system, especially when “causing problems” starts to include political activity.