Sorry to presume you are libertarian.  Your position is similar to many of that ilk.

Humans developed a need for fluoride, like many other micro-nutrients (such as calcium to which fluoride is chemically attracted).  How do you suppose that need developed if it wasn't via evolution?  Some god snapped his fingers?  

It boils down to this.  We have public health departments for just this sort of situation -- it is the job of these experts to guide the public on the science of public health issues such as fluoridation. Fluoridation is not a matter for city councils or the public at large who can't be expected to have a specialist's understanding of fluoride and fluoridation.