Remember that you can't yell fire! in a theatre for sh*ts and grins. And the First Amendment directly refers to government action. You might not get arrested for spouting offensive BS on Twitter, but you or more likely Twitter can easily face lawsuits for defamation, hate speech, or other expensive-to-defend-against actions. And juries love whacking the deep pocketed.

And Gresham's Law probably applies - Twitter under an EM regime will shed users and turn into an echo chamber. I guess there's money in this but I would think there's far more money involved in a milder, more generally used forum.