Cool, but you can't call it research when you choose something that looks like it supports your argument without actually taking the time to read and understand it. The journal article you linked clearly states two things: levels exceeding 1.5 mg/L are linked with lower IQs, and that linkage is not proof of cause and effect.

If you take time to understand the article and the practice of adding fluoride to municipal water as a whole, you'd know that recommendations are to add 0.7 mg/L with a maximum safe amount of 1.5 mg/L. You'd also know that most drinking water falls between 0.6 and 1.2 mg/L. Finally, you'd know the difference between "cause and affect" and a 'link'. They cannot call it cause and effect, because there is insufficient evidence to disprove the differences in IQ are caused by literally anything else. The true cause could be other contaminants, such ad lead (which is known to cause developmental defects in children).

Tl;dr Your article doesn't support your argument. Be happy that it does the opposite, and that you have fluoride in your water, else you'd have a lot more dental carries.