He has the right to free speech, yes. No social media, or hosting platform, is under any legal obligation to publish his free speech.
If he is spreading misinformation that goes against the sites terms of service, and actively leads to peoples deaths, then the site in question can revoke his access at any time. That is the site's f "free speech" in action, and you don't like it.
Idiots like to bleat on about the 1st amendment giving them the right to spout off whatever bollocks they want, wherever they like, but fail to realise that private companies and citizens have every right to tell you to shut the fuck up.