First, incitement to violence is not political speech. Hell, you've got CNN calling arson "just a political protest" (in other words, protected speech), but you think a tweet that calls for the authorities to do their job and protect citizens from rioters...that needs to be stopped because it calls for violence. You live in a strange world, where words mean the opposite of their normal meaning. Actual violence is speech, and actual speech is violence, in your world.
I suppose that demonstrates what a problematic issue this is. Maybe it is hard to decide what is a special case and what isn't. In that case, we should err on the side of allowing speech.