People blocked on Twitter are free to host their own websites with their own speech.

I really don’t believe just because Twitter is popular it’s suddenly mandatory that it host any and all content. If hacker news became as popular as twitter could the government suddenly start compelling HN to stop censoring off topic conversation and host any and all posts?

Twitter was created by people to serve a certain purpose and for certain conversations and they are within their rights to control the content they host on their machines and on their site.