See, here's the thing-- private online venues, regardless of size, have the right to moderate the behaviour of patrons however they choose. They have the right to establish a Terms of Service (TOS) agreement and if patrons violate that agreement, they can be removed.
This is actually part of the freedom of speech rights of those venues-- it would be a violation of THEIR free speech if they weren't allowed to ban people, even Donald Trump, for violating the TOS.
47 U.S. Code Section 230 is what makes this right explicit. It says that "the internet and other interactive computer services" (it was passed in 1996, if you're wondering about that terminology) have two specific rights:
They are not considered publishers of speech, which is to say, they're not equivalent to a newspaper staff who choose what pieces to publish and pay the writers for their work. This prevents private services from being sued for the speech of users on their platforms.
They have the right to moderate speech on their respective platforms as needed, and can't be sued by people who violate the TOS and get banned for it.
Now, it's definitely worrisome that right-wing extremists are using social media as organizing tools, but I don't think revoking Section 230 is the way to address that.
It might actually have the effect of forcing online private platforms to shut down altogether, because
a) If you're legally responsible for the content of speech on your platform, there's no way you could track all of the speech on that platform and analyse it to ensure that it isn't criminal (whether that means using it to organize for the purpose of nefarious activities, or posting defamatory or libellous content),
and
b) If you're not allowed to boot or otherwise censure anyone for any reason (aka, moderate), your platform will quickly become a place where no one wants to go. It is not, actually, true that the best solution to awful speech is more speech, especially if the people who would be speaking "more" are sick and tired of the awful speech and don't want to see it anymore.
Anyone who has tried to manage an online (or offline) community knows this-- if you let the assholes stick around, pretty soon all you'll have are assholes.
And if the platform is legally responsible for the speech of assholes, pretty soon you won't have any platform.