It's not a "lunatic" thing. It's an acknowledgement of trade-offs in medicine. Everything you do in medicine is a balance of benefits and risks. She's just applying the same logic to this.

In her medical opinion, preventing cavities and thus allowing people to keep their teeth longer, so they can chew and eat normally without requiring thousands of dollars' worth of oral appliance is worth the risk. Further, cavities also carry a risk that oral bacteria can get into the blood and heart causing some of the most deadly infections we know of. She wants to reduce that risk as well. For her, she thinks of the worst case scenario and makes the trade. That's what she recommends. Dentists do the same, which is why you've heard your entire life about the benefits of fluoride to fight cavities.

Why people on this site feel compelled to act like the whole world is trying to screw them and that there's some massive conspiracy that they teach in medical schools is beyond me. It's total horse crap, and it's a total misunderstanding of what the whole Q thing is about.