It's been argued time and again, from one side that Facebook and Twitter are private companies and that free speech doesn't apply on their sites, and from another side that what we're talking about is an abstract principal of free speech, not the legal definition.
But if you remove the loaded term of "free speech", what's actually being discussed here is "website moderation policies". With that framing, what is the expectation for Facebook and Twitter? To devolve into 4chan?
Personally, I like well moderated sites. That's why I'm here! It's bizarre to me that so many other people who chose to spend their time here expect Facebook and Twitter to be laissez faire about moderation.