Interesting. The article doesn’t actually say that fluoridation in water supplies is dangerous but that some researchers are questioning. Generally code for lack of scientific evidence. It also finds that early studies may have had a flawed basis (pretty much all early studies have been found wanting by later scientists) but doesn’t refute the results.The study mentioned in the article talks about high levels of fluoridation which I assume is in lab tests however these levels are not the case in water supplies.
The correct way forward is more actual science based studies.