I do not know much about fluoride, except that every dentist I ever talked to and the Centers for Disease Control are in favor of water fluoridation. While fluorine is a toxic gas, the fluoride in water is a salt. The main danger is the emotional distress caused by attitudes like some letters.
Many letters have been printed opposing introduction of scientific discoveries, such as bio-controls, or GMO crops. Almost invariably these letters equate the proposal to invasive species introduced in the, mostly distant, past: mongoose, Christmas berry, rabbits etc.
What the letter writers appear ignorant of is that those introductions were made for selfish reasons without any science at all.
There is a popular culture that has come to distrust science, and instead accepts anecdotal evidence (true or not) to reject: fluorides, vaccination, pasteurized milk, nuclear power, seat belts, geothermal, GMO, windmills, helmets or anything else they heard a horror story about. This happens in spite of overwhelming scientific and statistical evidence that the benefits outweigh any risk. I guess the world needs boogeymen, even if they are imaginary.