New age medicine has been around forever, yes. But the effects are only known to be negligible outside of pandemics. We know from history that people did many irrational things during past pandemics due to fear and social contagion.
It's a tough problem, everyone believes themselves an expert on everything, plus trolls and disinformation campaigns. There's also a significant information asymmetry.
It's funny you mention opioids as I just recently came across a tweet claiming that Indians were responsible for getting Americans addicted to them via prescription. In one of the buried reply chains, the poster admits they have no evidence and are just repeating a claim someone made to them sometime. But how many people will read that initial post and reinforce their racist beliefs vs see that the claim was unsubstantiated? And when that leads to drastic action by a madman, who's going to be the target of the blame? The responsibility is too diffused to target any specific person, the government obviously won't, madmen don't act in a vacuum and so the blame falls on the platform.
Yes, no one should have the power to determine what ideas are and are not allowed to propagate, but on the other hand, you could still go to other platforms and are not entitled to the reach of the major platforms, but then again, these platforms are extremely influential. At the same time there's also the problem that people in part view the platforms as responsible when they spread bad ideas, the platform operators also feel some level of social responsibility, while the platform owners don't want legal responsibility.