Didn't the court rule against infant circumcision, and not circumcision itself?
Irrelevant. It's still a significant infringement on religious freedom, and cannot be tolerated.
Is that more important than genital mutilation?
Describing male circumcision as genital mutilation is vaguely insulting to people whose genitals have actually been mutilated in a meaningful way. If anything, adult male circumcision (or even mid-to-late childhood) is a lot worse than infant.
So having the foreskin of an infant removed at the wishes of a parent is not meaningful mutilation? The British Medical Association has declared that it carries 'medical and psychological risks.' Should we just ignore that opinion?
You are supposed to have a foreskin. It's there to serve a purpose. Just because some think their god wants it shorn off doesn't mean we should tolerate it if the state and medical professionals oppose it.