Earlier quoted context omitted.
That analogy doesn’t really fit with the model of Twitter. If we are using the town/time square example, what Elon is describing is the digital version of putting a noise-cancelling box around the people saying “bad” things so that nobody can hear them. A message spreads on Twitter because individuals on Twitter amplify it (with engagement, retweets etc.) which is itself a form of speech: if you say something bad, an…
Twitter is half a content delivery app (getting tweet from you follows) and half a content suggestion app (tweets TW thinks you might like) In a charitable reading it looks like Elon wants to remove hateful speech from the latter and leave it off the former. This will allow you to say what you want and to follow who you want. Who ends up in your suggestions has nothing to do with free speech.
If the postal services decides to ban you from this "papers you might like" service you are still allowed to send as much mail as you want to whoever you want, but you no longer have access to the postal service expertise in spreading your news.
This can obviously be abused but it is also very different from being unable to send any mail at all.