I'd say that behavior is similar to if an individual in, say, a school or assembly, shouted "FIRE" upon witnessing a chemistry demonstration involving a controlled flame. If that somehow caused a stampede resulting in loss of life they might be held accountable by the courts. These acts on social media can be quite similar philosophically, so one would expect that the legal treatment should be similar (albeit perhaps adjusted proportionately for impact and reasonableness of the held belief).

I don't necessarily think that's what should be done in practice, but it seems consistent with how western society responds to this behavior in other settings.

I don't necessarily think there is a good solution, either - I just mean to say that people who do that, even if they are well-meaning, are behaving unethically. That's because they believe in their own perspective with 100% probability, but that's obviously unreasonable from a Bayesian perspective. If they accounted for even a small probability that they are wrong then their behavior would change dramatically.