>Social media companies have argued that they cant be held liable for things posted to their platforms in the past and have tried to position themselves at neutral platforms. When they start to become the arbitrators of what is and is not to be posted they are no longer neutral platforms like the phone company.

Social media companies don't become more liable just because they moderate. They all do that already. There's no sudden legal line between moderation involving messages with spam or bigotry.

I think anyone amplifying messages on a large-scale in a one-to-many manner, between people that aren't equally engaged in a conversation together, should be considered to start accruing responsibilities over the content of what they're participating in amplifying, in a way that a phone companies largely don't have. I think social media companies have been largely shirking that responsibility by phrasing it as a free speech issue and letting anything go.