It really is very simple. The golden rule is all we need. Your rights end where my rights begin. Do anything you want to your own body in the name of religion but leave me and my body out of it. It is illegal to circumcise girls in the USA for religious reasons. Boys should be afforded the same protection. The owner of the penis should get to decide its fate.
The baby should be considered to have a right to genital integrity, bodily autonomy and self-determination. The baby's religious freedom must also be considered. The baby of course can have no religion until it grows up and makes up its own mind. But say it grows up to reject the religion of its parents? Perhaps the child will become an atheist and want to keep all his body-parts. Perhaps the child will become a Sikh and be opposed to all body alterations.
We must start considering infants and children as individuals in their own right and not the property of parents or the state. Parents have certain rights with respect to how they raise their kids but they also have certain responsibilities. One of those responsibilities is to protect the child from harm and abuse. Circumcision for cosmetic or non-medical reasons is an unprovoked assault upon the person and the psyche. We recognise this instantly when it is done to little girls. Boys should be afforded equal protection under the law.