Fluoride in the drinking water stained my little brother's teeth, he has yellow-brown patches on his front teeth that'll never go away as long as he lives, and the dentist says his wisdom teeth will have to be surgically removed before they all even start to emerge because one has a weird shape for the same reason. Sure, fluoride can be good for some people's teeth, but there's a subset of the population that has genetic sensitivities and it causes them problems. Whether you believe it causes other problems or not, it can atleast cause these kinds of issues, so it is an issue of the many vs. the few no matter how you slice it.