Cigarettes are mass manufactured and widely used for quite some time. Its recently been found that some fake sugars may give you a massive boost to your chance to have your brain rot via Alzheimer's. Asbestos was widely used previously as was leaded gas was everywhere decades after it was widely known how bad it was. Not being banned his historically been a really bad predictor of safety.

I linked to a whole list of people that died or suffered via trusting alternative medicine. Anyone wanting further info can check out https://en.wikipedia.org/wiki/Homeopathy

Honestly though one shouldn't need to fully explain that homeopathy isn't real in the same fashion as its usually not required to explain why witchcraft, literal magic, young earth creationism, or voodoo isn't real.

I'm not trying to convince anyone silly enough to believe, I'm trying to discourage people from promoting it as benign.