It's totally reasonable to be sad about this. It pattern matches to a loss of free speech, and when society sees free speech being violated, it should evoke strong emotions (hopefully even more severe than sadness).

This is not, however, a violation of free speech, even if you believe in the general concept that a private company should allow dissenting opinions on its platform. This user has violated the "yelling fire in a crowded theatre" exception to free speech, which even the most ardent supporters of the concept admit is important to protect.

These private institutions aren't perfect, and judging if speech breaks the one exception to the moral concept of "free speech" is hard. We'll get it wrong. The alternative, however, is to let the panic incited to occur unabated, which seems substantially worse.