Some Anglosphere countries (USA, Canada, Ireland, Australia) love to add fluoride in water. They say it’s good for people’s dental health.
Europeans (Germany, Finland, Italy, France, Netherlands, Switzeland) think it’s wrong/unethical.
There is actually regular controversy around this
https://hsph.harvard.edu/news/fluoridated-drinking-water/
Do they put fluoride in your drinking water ? Are you happy with that?
There’s regular controversy around the age of the earth, the shape of the earth, and whether astronauts have ever been on the moon.
The Harvard article mostly talks about whether fluoride helps adults. The safety concerns are mostly about fluorosis. That has very specific symptoms on the teeth themselves, and if you see it you should be investigating whether someone is swallowing lots of toothpaste first.
You will see a lot of crappy medical science touted by universities. Many of their hospitals offer “alternative and complementary” medical treatments because people are willing to pay for them. Scientific consensus from experts and what you can find some kook supporting are not the same thing.
The neurotoxicity study from Mullenix doesn’t have teeth (pun intended), and the people who keep touting it 30 years later might as well be flat earthers.