The steroids thing is a great example that shows that “we” don’t know things. Even when the information is out there some don’t have access to it and some don’t believe it. For every pro bodybuilder or shredded Hollywood actor using steroids (many, to put it lightly), there are tons of people following their routines and diets, thinking it will lead to similar results. Not all that much research and critical thinking will show that that’s not going to happen.
This isn’t really an answer to your question, but the bummer is that even someone like the people you listed telling the truth isn’t enough. Shit, tons of people still believe the thing about carrots.