Earlier quoted context omitted.
Facebook is also not preventing anyone from speaking to me; they are refraining from giving some sources a megaphone. If I want to know what the BMJ is writing, https://bmj.com is right there. Facebook is under no obligation to center it on my wall.
"A government that censors the press is also not preventing anyone from speaking to me; they are refraining from giving some sources a megaphone." "refraining from giving some sources a megaphone" is exactly equivalent to "censorship". There's no difference. Your argument confuses the prescriptive and the descriptive. Descriptively, yes, Facebook is under no legal obligation to treat speech on its platform equally. P…
Under the political theory underpinning the origins of the US, private institutions have different moral obligations from governments because governments have the monopoly on violence, not simply because governments are big and have lots of "users." Facebook can't force anyone to use Facebook, and their competition is always one click away.
Facebook isn't a "public square" because it has no local geographic monopoly on space; it's the Internet, we have our choice of internet fora. This differs from the physical world, where one can't easily just go to the next public square over if the use of the nearby one is curtailed (hence the need for legal theory enacting the concept of "de-facto public square"). There's a problem if Facebook is the only online forum. But the solution to that is anti-trust law, not the government dictating what Facebook may not refrain from rebroadcasting via its network. Trying to solve the legitimate concerns of discourse manipulation via modification to First Amendment protections opens a Pandora's Box that is almost certainly best left closed (for starters: given the customer behavior we currently see, one could infer that people use Facebook because they like the signal-tuning. Stepping on the neck of Facebook's ability to signal-tune in a heavy-handed way risks driving users to alternative services that don't operate out of the US and therefore aren't beholden to any concept of First Amendment protections, for good or ill).