I'm not sure but it's certainly one to think about.
I suppose it could be argued that a child with (for example) a large imposing facial birthmark, may become very shy and withdrawn which could shape the rest of their life as an adult, but there's no guarantee that will happen. The parents however, may not want to take that risk - thinking that perhaps by the time the child is old enough to have it removed, they may have suffered socially. Therefore they may feel as though they are making a decision that's in the child's best interests, welfare-wise.
Compare that to parents who have chosen to follow a certain religion/practise a certain culture, and therefore decided their baby will also have to do the same (until they're old enough to decide), and you're left with the fact the baby had part of their body removed - not for their own welfare, but for a religion that they had no say in joining.
It's a far cry from tipping some water on their head and sending them home with a certificate for example.
The water will dry, the certificate can be ripped up but the foreskin cannot be sewn back on.
So in whose interest was the foreskin removal? I would say it was definitely done in the interest of the parent only, who chose to follow a religion/cultural practise.