But yet I'll note they did stop at preventing punishment for speech, but infringing it all. Because at the time, the only force big enough to do that meaningfully was government.
This is moving far afield of the topic, so I will only briefly address this. From a historical perspective, this is incorrect for the following reasons:
1. At the founding, there was a robust debate as to whether the First Amendment applied to only restrictions on speech (what we would call prior restraints), or also applied to punishments after you spoke. This issue was left unsettled for some time.
2. In addition, this was a specific restraint on the federal government; it did not apply to the states until much later. While some states protected speech, many did not.
3. Finally, almost everything people think about the First Amendment is the product of 20th Century judges; even through the late 19th Century, it was considered unexceptional for the government to restrict speech (for example, censorship by the post office).
Regardless of any of this, Umbran is correct- having a private platform not carry your message doesn't meaningfully restrict your ability to speak. Choose a different platform.
EDIT- to move it back to the topic, it would be a shame if SnarfBook was forced to carry Covid Misinformation because I had to "both sides" everything, regardless of what I wanted.