The legal mechanisms to do so are there. They’re called libel laws. But the DoJ is too weak to use them. A dozen misinformation spreaders were responsible for 2/3 of the anti-vaxx misinformation. Shut them down and prosecute them under RICO law that allows for the seizure of their assets during trial. This law was used against the KKK and the mafia. Putin’s RT and Internet Research Agency spread anti-vaxx idiocy in both eastern Europe and the USA as part of Russia’s export of its kleptocracy: https://www.hudson.org/research/16608-countering-global-kleptocracy-a-new-us-strategy-for-fighting-authoritarian-corruption .