Going even further, another way to interpret the 1st Amendment is that it is the federal governments responsibility to protect those freedoms, and that it would be well within the power of Congress to enact laws prohibiting the censoring of free speech, even on so called private platforms. This sort of thing has been done in the past, for example by prohibiting discrimination based on race even in private establishments.
Actually, I don't think this is a valid interpretation of the First Amendment, which is written specifically to circumscribe the powers given to Congress, beginning "Congress shall make no law..."
