Afaik these findings primarily involve populations exposed to fluoride levels above 1.5 mg/L, which is higher than the 0.7 mg/L recommended for U.S. water supplies. There is insufficient evidence to conclude that fluoride at recommended levels negatively impacts IQ.

At safe levels fluoridation is a public health measure akin to fortifying foods with vitamins (e.g., iodine in salt or folic acid in flour something we do all the time).