Also, very classy of you to paint me as "anti-fluoride" like I would have to have some sort of agenda to question why things are being added to drinking water.
Please abstain, all of you, from acerbic swipes at one another. Both sides are to blame here.
If you must dispute water fluoridation on Hacker News, do so by making careful, factual, respectful comments.
The site guidelines specifically ask you not to call names. That includes both calling each other names as well as calling each others' arguments names (e.g. "woo").
Public water fluoridation has well-understood health benefits (a reduction in cavities that cannot be achieved through brushing alone). It also has well-understood drawbacks (tooth mottling in high concentrations, toxicity in high concentrations).
Someone participating in this discussion would either know this from general knowledge, or could look it up.
It's trivial to find sources for the effectiveness of fluoride in preventing tooth decay (Google -> Wikipedia -> a citation leads you here: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm). There are also studies on water fluoridation's impacts, though it's harder to test that, by nature.