I was curious, so I did the research you asked us to do. My best understanding after about 30 minutes is that historically, experiments examining fluoride neurotoxicity involve fluoride levels far exceeding the regular consumption of North America and elsewhere as provided in the water supply, so it's hard to get an understanding of the possible health effects.
There are more recent studies regarding this, however, that do indicate some level of toxicity to the brain in lower doses. Again though the data seems to conflict at times and requires more study. Here's a nice link for more reading.
You came in here making conspiratorial accusations about the government and invoked some aetheric "what about the animals" nonsense and provided no material to support your position so idk why you're confused about how you're being received here. Fluoride is indeed helpful in preventing tooth decay, so you're gonna have to do some more work than the tired old "Do your own research."
You're claiming it's bad. If you don't understand that you need evidence to back up a claim, it will be impossible to argue your point. You're free to continue shouting into the void if you want, but until you take this at least as seriously as I do (not very I may say, my research was very brief) you're going to continue getting downvotes. I'm just telling you why here. You sound like a crazy person to the average lurker.
They did in fact prove that fluoride stops dental decay. Now it's your turn to prove that there's a negative side effect that outweighs the positive.