Right. We're probably all aware of the text -- this is a US-centric site, after all. But I think you make the GP's point all the more necessary: The first amendment to the US constitution restrains one party from introducing rules abridging freedom of speech. There are plenty of other parties who may or may not seek to introduce and/or enforce rules allowing or prohibiting various forms of speech which are not the US government. My own government, for example. And Twitter.
That an action doesn't breach the first amendment to the US constitution doesn't say all that much when it comes to whether it's consistent with the stated ideals of proponents of freedom of speech.
That an action doesn't breach the first amendment to the US constitution doesn't say all that much when it comes to whether it's consistent with the stated ideals of proponents of freedom of speech.