False logic, Bob.

All water treatment processes are implemented to protect the health of those who drink it.  An increased risk of dental decay, while not as dramatic as an increased risk of diseases transmitted by pathogens in the water, is still a negative health effect.  Seriously, is an increased risk of tooth decay something you would wish for yourself, your family, friends and neighbors?

Fluoridation opponents arbitrarily define water treatment to promote their anti-F agenda, and don't understand that "fluoride also interferes with glycolysis, the process by which cariogenic bacteria metabolize sugars to produce acid." (2016 WHO report, Fluoride and Oral Health.  In other words, like disinfection it acts on bacteria.