To be fair, 'free speech' isn't even something a company can force themselves to follow. Short of selling to the US Government (who would have to explicitly accept such an offering), being bound by free speech isn't possible without making your own rules for what qualifies as free speech and what happens when the platform 'violates' it - ie. you can't say "take all matters of violating your first amendment to civil court" since corporations, by design, cannot violate your first amendment rights.