If you go to a bar or a park and play loud music over everyone, or amplify your voice loudly enough to try to have a conversation with everyone simultaneously, then they can kick you out. These locations can define their range of acceptable behavior, and that usually includes a lot of norms about socializing and letting people in their own subgroups be free from egregious distractions. Social media can similarly construct and define its own norms. No single location or specific social media site has a monopoly on speech. We have a large choice between them, and especially online, the barriers to creating your own space are low.

Already on Facebook, I generally can't make a post that's shown to other people automatically who are disconnected from my friend group. Is Facebook limiting my free speech by doing that already? Hypothetically, if Facebook did stuff like decreasing the volume, er, show rate, to far-away people if my post is re-shared from my friends and so-on to very far outside of my immediate friend group, is that then censorship?

On social media, people choose who to listen to so nobody can "play loud music" to those who don't want to hear it. Censorship is to protect people from wrong-think that they want to hear, not to protect them from what they don't want to hear.