[hammock]

Iodine and fluoride aren’t really the same thing.

Iodine is essential, you cannot survive without it, and it is added to supplement a deficiency.

Fluoride is not essential, you can survive without it, and its addition is purely therapeutic, not due to some deficiency

[epgui]

As a biochemist, I know this perfectly well. But the motivation behind your “this is terrifying” was left as an exercise to the reader, so there was no way of distinguishing it from “omg the chemicals”.