I think you may be misunderstanding the post. He is not saying that Meta is prohibited from censorship by the First Amendment.
He is saying that the US has free speech norms (not laws) where it is acceptable for people to get together and rant about X, Y, or Z. There are limits (e.g. calls for violence), but they are few. Anyone who does not like the speech can leave the room, try to argue with the speaker, or make their own speech in another room. It is not the social norm to shut down the speaker, make the speaker unemployable, trash or bankrupt the venue, etc. Those actions are contrary to the norm.
That is simply not true. One example is a hilarious skit by an Australian comedian (John Safran) going to salt lake city and knocking on doors asking if he could talk to people about atheism. The amount of violent threads he received is quite revealing.
In my personal experience having lived in the US and several other countries, I found officially people can say much more things (i.e. due to the strong freedom of expression laws), but in personal settings you are much more likely to be shut down, fired, threatened with violence, ostracized... for stating unpopular (in that social environment) opinions, in the US compared to the other countries.
Meta is a private organization[1]. It is not “the US.” In fact, most of its customers aren’t even in the US.
Private organizations dictate their own social constructs. It’s not acceptable to proposition sex at a book club, but it’s acceptable to do that at a swingers club.
This idea that private companies follow the social norms in the US is only partially true at best.
It’s socially normal for me to talk about how my company sucks and I hate my boss with 100% of my friends and family, but doing so at my place of employment isn’t okay. That’s one major example where my company doesn’t follow social norms.
If what you say is true then YouTube should allow hardcore pornography since over 90% of men watch pornography. It’s socially and legally acceptable, with numerous legal brick and mortar businesses specializing in that market. But they don’t allow that because they are a business that doesn’t want to engage in that business activity.
I think it’s easy to mistake the current state of private social media as “open” in the way you describe just because it looks open. To your point, not a lot of speech is banned outright, which seems parallel to US social norms, but whether or not something is banned or removed from social media is almost meaningless because promotion and multiplicative reach is the domain of the algorithm.
The algorithm doesn’t promote and multiply the reach of content based on whether that content is most aligned with social norms. It’s promoted based on whether it makes money or causes users to stay watching the platform.
In real life, you don’t hang out with your friends and family most who make you the most mad or generate the most shocking content. But that’s how social media works because social media isn’t real life.
This idea that today’s social media platforms are a neutral vessel for speech is flawed right from the start because of that algorithm.
[1] publicly traded, private as in “private property”
Facebook wants to get that speech in as many rooms as they can, because they figured out a way to profit off of the emotional reaction of the people who were already there. They offer free hosting for community groups of all sorts in order to bring people to the rooms they can profit from.
He is saying that the US has free speech norms (not laws) where it is acceptable for people to get together and rant about X, Y, or Z. There are limits (e.g. calls for violence), but they are few. Anyone who does not like the speech can leave the room, try to argue with the speaker, or make their own speech in another room. It is not the social norm to shut down the speaker, make the speaker unemployable, trash or bankrupt the venue, etc. Those actions are contrary to the norm.