Earlier quoted context omitted.
i also thought about that. But a society sets the rules businesses operate in, that ranges from environmental laws to other regulations. I think its perfectly valid to also set anti-censorship rules if the society think its valid.
Freedom of speech includes the freedom to not say something. It would require a constitutional amendment for the gov't to come in and start demanding things from Facebook.
But i don't think there are major obstacles to introduce such law in germany/europe. We already have media-laws and special press-laws (which regulate how stories must be published, for example we have a "journalistic duty of care" which amongst other things mandates that unconfirmed statements must be marked as such. The law follows the codex of the German Press Council).