Don't conflate the broad concept of free speech, with the specific attempt at its defense that is the 1st amendment of the US constitution.

Giant unaccountable companies privatizing the public square harms free speech. Forcing them to at least reveal why something was censored would help free speech more than it would harm it. Unless you subscribe to the myopic legalistic 1st amendment position that "free speech" is maximized when companies can act with the least restrictions, no matter how unable to speak or be heard that makes individuals, so long as it wasn't the government that silenced them.