Well, I’ll bite. 
I actually did quite a bit of research on this issue some years back, for my own edification. There actually ARE some valid, reasonable objections to fluoridated water supplies, and flouride in general. For the record, I examined a wide variety of sources, so I’m familiar with the so-called conspiracy theories as well as with the peer-reviewed studies and scientific facts.
Fluoride is a toxin, there is no debate about this. The only debate is how much is too much.
Fluoride falls above lead and just below arsenic wrt general toxicity, and is a cummulative toxin, as is lead. Yet the allowable levels for fluoride in drinking water are over 200 times those for lead, last I checked. ( 0.015 ppm for lead and 4.0 ppm for flouride).
Even at lower dosages, there are many who can potentially get too much, because tap water is not the only source.
Many canned foods and bottled juices/beverages contain fluoride, as do most dental care products of course. It also occurs naturally (in its natural form, which differs from the form added to water and dental products, ftr) in some foods, the quantity heing highly variable depending on the type of food and where it was grown. (Colorado and Texas, to name 2 areas, have fairly high levels in the soil. Spinach, for instance, contains among the higher levels of naturally occuring fluoride, as does black tea).
Further, fluoride is an industrial pollutant (used in, among other applications, glass etching and the alluminum industry). Depending upon your location, you are exposed to varying levels through air, water, and soil contamination.
Perhaps the biggest variable has to do with differences in voulme of consumption/exposure relative to body mass. Some people consume far more water (or other flouride containing foods or beverages) than others. Children are far more likely to get much higher doses relative to their body mass, both because they are smaller but because they tend to consume more bottled juices as well as to injest more toothpaste and even be given fluoride tablets at home or school.
Ingestion of toothpaste is a common cause of poisoning in children, and a single tube can result in death (and has). Short of that, over-exposure can result in permanently damaged teeth (fluorosis, characterized by yellow or brown discolorations and fragility) and other symptoms of accute poisoning. Why tubes now carry a warning label…and why, imo, childrens’ toothpaste in enticing flavors like bubblegum should be banned! Yes, kids WILL eat it.
There is no evidence that ingesting fluoride past the 7 or so years of age has any beneficial effects on dental health, yet everyone is dosed. One of the documented effects of excessive fluoride consumption is damage to the skeletal system (brittle bones), and yet the elderly, who are at higher risk for this condition and stand to gain no benefit in terms of dental health, are dosed as well.
Other known results of long-term, higher dose fluoride exposure include bone and reproductive cancers.
It is, imo, simply irresponsible to attempt to deliver medication via the public water supply. Not only can the dose not be controlled, but it amounts to forced medication and carries risks, esp. to those more suseptible (risks which, again, cannot be controlled for due to the blanket nature of the practice.)
It is also debatable how much if any benefit to dental health exists, even when used at proper doses, and the early studies used to promote fluoridation have been challenged due to their methodology.
Anecdotally, my late husband and I were both raised with fluoridated water and toothpaste and we both had/have a mouth full of fillings. I didn’t STOP getting cavities until I was in my 20s and STOPPED using/drinking fluoride. I also have some brown discolorations on some molars due to fluorosis (diagnosed by a dentist).
Neither of my kids have ever drunk or used fluoride (aside from the infrfequent topical treatments at dental visits, which I allowed once they were old enough not to swallow any) and their teeth are great. My son, at almost 18, has had 2 tiny carries, both minor enough to be air-abraded, and my daughter, at 10, has had 1, in a baby tooth, which did not require treatment.
Our city does not fluoridate and I am glad…I do not want medication, ANY medication, in my drinking water. I am quite capable of procuring and using fluoride containing products if I choose to, and the schools here offer fluoride tablets to all students (unless parents sign off, which I do).
