I think it's entirely a personal choice and I have no problems with parents who want to pierce their babies, toddlers, or pre-school age kids.
I would have problems if they were piercing anything except ears though....lo. Didn't think of that one I bet.
To be honest, who's going to police it? I can heat up a needle and poke a hole in a kids ear if I want to poke a hole...taking away the ability to go to the store and get someone who knows what to do and how to do it quickly and sanitary....well, why in the world would anyone want to take that away from anyone?
If a parent chooses to pierce their child's ears no one has the right to tell them no, no one. That is their child and they have the last say as to what happens to them, I think there ARE extenuating circumstances that takes that right away though. If a child is sick and in need of medical treatment and the parents refuse to seek medical care then there needs to be a legal way for the state or someone to step in and seek treatment for that child. IF there is a team that includes the parents so they can be heard then the child can receive the best options to help them heal if at all possible.
Other than those life threatening situations a parent has the right to do what they want. Piercing a kids ears is a silly thing to make laws about.