If they are still listening, tell them to avoid the internet and talk to a doctor.

That's exactly what I did. But it's also some of the other friends who pressure them. Earlier this year I got a desperate call from a long term friend perplexed about the "myth" the "fake covid  scam" was causing , after trying to engage in a reasonable discourse over his claims, I will say with 100% accuracy that he will never talk to me again for the rest of our lives. Even cousins which I have been a supporting part of the family  now alienated.  

Just as a virus spreads in proportion to the number of infected people, so does misinformation. Social media has the equivalent potential to magnify it as does a super spreader event.

And then you have elected officials helping that misinformation along.

Yeah, a real mess isn't it?