Disinformation (spreading false information that you know is false) is illegal in the US [0]. The question isn’t whether people should be free to knowingly spread false information. The question is who should decide what is false information.
Giving a single billionaire the power to decide what speech is allowed (and what isn’t) is dangerous. No individual’s incentives align with everyone else’s. And the wealthiest person in the world has especially unique incentives.
If we want to align our social media platforms’ rules with what’s best for society, then we need society to decide the rules.