Greenwald seems to have some difficulty understanding the First Amendment. He needs to re-read it:

****Congress shall make no law**** respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press…

The First Amendment makes NO guarantee regarding the absolute freedom of you or me to say whatever we please wherever we please. It simply says that Congress can't shut us down using its power to write laws.

The owners of content distribution channels can moderate however they see fit. If they want people to only discuss the merits of the platypus, and nothing else, they can do so. If they want to kick Greenwald off their platform for trying to bully them with his opinions, they can also do that. It has nothing to do with the First Amendment. Free speech in and of itself is not guaranteed constitutionally in that manner.

Greenwald is welcome to say whatever he wants, but he can't bully his content distributor into following his wishes.