@flo We’re still not quite sure exactly what you want to know.
It is possible that a “quack doctor” (one that is either not legitimate, or is doling out dangerous or unhelpful advice) could give SOME good advice, along with the bad advice. Sure, that is very possible.
Do you think that telling people not to talk on their phones while driving, or telling people that smoking is dangerous, is reasonable advice? That’s the part I’m having the most trouble with. I’m not sure if you think those 2 activities are bad/dangerous.
I also simply don’t understand the part about the “quack”. What is YOUR definition of a quack?
Are you wanting to know if bad doctors also sometimes give reasonable advice to some people, some of the time?
Or do you want to know if regular (non quack) doctors give advice that seems redundant or possible wrong, to you?
We all want to answer this question, but I know that I am having a hard time figuring out what the actual question is.