It's not intended to fix all dental issues. Its purpose is to decrease the amount of tooth decay in the general population, particularly in children. And in that goal, it has been wildly successful. Also, the miniscule amount of flouride used in the water supply has no adverse impact on animals, nor does it interfere with beer brewing. So, I don't think those arguments are particularly compelling. 

The one argument I consider valid and worthy of debate is the matter of flouridation conflicting with notions of informed consent, and the imposition of flouridation on persons who specifically don't want it. Given that the scientific consensus is firmly on the side of flouridation, and that its safety and efficacy has been roundly established in the nearly 75 years its use has been official US policy, I think the matter of informed consent would be the most productive, and intellectually sound argument to focus on.