Looked into this some years ago, in the early days of the web. Their claims, fwiw, were that flouride as used in municipla treatment plants is a waste product of the aluminum smelting industry. As if that means anything, I dunno. If recall correctly, the nutjobs don’t dispute that teeth enamel is preserved, but that it causes other harmful effects to the nervous system? I dunno.
It works - my dad, who is 82, has virtually none of his teeth left. Myself, never had a dental carie! Never been too particular either, and bottle caps are no problem.
One angle, might be worth pursuing, that the mandatory addition of anything to the public water supplies might be questionable, even if it’s for “our own good.” I can see that, sort of - but disinfection is widely done and nobody complains about that. And - think about this - Dentists recommend it, which in fact over the decades has decreased their income, probably substantially. All in all, the whole debate doesn’t make any sense, unless flouride reliably turns out the boshie in all of us. /s
That was one of the early indicators I caught they didn't know what they were talking about was they didn't know the difference in the different fluoride compounds*, the 'toxic' byproducts are not the same fluoride as used in water treatments. (*sodium fluoride and sodium monofluorophosphate are safe and used in water and dental fluoridation; acidulated phosphate fluoride and stannous fluoride are different compounds and are the toxic versions)