I don’t think Twitter is wrong, and it is not really different from Apple not letting pornography into the App Store, but it is still deeply troubling to me at some level. And it is neither moderation like discussed in the article or censorship as discussed in the article.
And that's the precise point at which they cease to be a "middleman" and become a publisher.
Nobody argues that owners of physical premises should choose between accepting full responsibility for every action on their premises or being utterly powerless to eject any person for any reason.