Your Random Human Rights Reminder

Given today’s xkcd cartoon:

I wanted to reiterate the point in this post.
“Free speech rights” and “the First Amendment” are not synonymous with each other. The First Amendment is the American legal manifestation of the right to free speech, but the right exists outside the United States and existed before the first amendment. The Founding Fathers were well aware that they were protecting an existing right with the First Amendment rather than establishing a new one.
Nor do all manifestations of the right to free speech include the First Amendment’s limitation of that right to government actions. The Universal Declaration of Human Rights, in Article 19, talks of the right to free speech without any reference to government:

Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.

Since the United States voted in the United Nations in 1948 to adopt the UDHR, in fact, you could make a free speech argument in the United States about the actions of a non-governmental body by invoking the UDHR rather than the First Amendment.*
Why is this important? First, because we need to be clear that human rights are universal and do not depend on nations for their establishment. The point of human rights is that they are the universal inheritance of human beings, not to be given away, outlawed, or otherwise abnegated by other humans or their governments. This may not work out well in practice, but it is the goal to which to aspire.
Second, and this is true in the United States, large corporations have the ability to silence their critics in a variety of ways, like SLAPP lawsuits or confidentiality clauses in court settlements, and we should not dismiss these actions as not being about free speech simply because the First Amendment does not apply.
Human rights are not, and never have been, simply the sum of what the Constitution gives us.
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*It would be interesting to know if, in fact, this has happened.