Can circumcision be done enutero? If so, just use their abortion argument against the regulation. (”My body my choice(sic)).
Once born, they are a legal entity, a U.S. citizen - and the government has ‘a compelling interest’ in prosecuting you for damaging it.
Now I don't think circumcision is damaging, usually people want the kid to be like his father, or have health, aesthetic, or religious reasons for doing so - but I figure that is the argument these wackos are making - that it is akin to female genital mutilation - which is absolute rot.
I say this as someone who is quite happy with being intact.