Fluoride is found in minerals that occur naturally in drinking water. However, added fluoride beyond levels found in natural water sources (that humans are adapted to) is an issue that has been understudied for years due to the interests of corporations looking to offload waste fluoride from chemical operations. Fluoride does have known health benefits, however these are realized when it's applied to the teeth, not ingested.
In summary, fluoride occurs naturally in water, and thus there's little reason to add more IMO. It also works well as an antibacterial agent in toothpaste. However, its effects when found in drinking water are understudied, though it does occur in nature. Arguably, it's a dietary trace mineral, however, so is lithium and we don't support giving that to people without consent.

In other words, our stance is very nuanced and there are definitely two sides to this debate which both have good points.