I'll be happy to answer you, Top Cats Hat:
Yes. Bad taste joke, but I'd defend their right.
Yes, if the misinformation doesn't come from medical professional/organisation. The biggest problem in this case are people believing the misinformation, I'd personally propose other mechanisms to fight this than taking someone's right to spread (even false) opinions.
Yes, if there's no crime committed (e.g. threats, stalking, harassing, ...)
Again, yes, if there's no crime committed.