I wrote a long post but it went poof. Gah.
Anyway: their reasons, not there.
Any rational person must know at an intellectual level that we make thousands of decisions for our children, before they are able to consent. We do that on a risk-benefit assessment basis, even though this doesn't necessarily rise to a conscious level. Should I let my baby cry to sleep, or go and pick her up? Should I give my child a dummy or not? Should I drive the baby to the supermarket, or walk there? Should I send my kid to a nursery or a childminder? Which if these is safest? Which will procure the most long-term and/or short-term benefits? We do this, literally, ALL the time. Many of these decisions will have an impact on our children's physical appearance: what we feed them will impact their weight. A dummy may impact their teeth. Letting them climb, cook, ride a scooter may improve their physical skills, but they may also hurt themselves in the process. The BCG vaccine will leave a scar. We assess risks and benefits, and make the decision that we think is right. That different parents make different parenting choices is a consequence of the fact that they face, and perceive, risk and benefit differently, and that they are influenced by their community, upbringing, personality, etc. What seems a good parenting choice for a person will be deemed a risk not worth taking by another.
Scientific evidence shows that the benefits of infant circumcision outweigh the risks. Therefore making that choice is not immoral, unreasonable or misguided. It may not be what YOU would do, but you are not walking into everyone's shoes.
But of course this won't matter to you Curlew, as your mode of argument can be reduced to the following: if someone disagrees with you, they are misinformed and brainwashed. If someone finds you offensive, it's because you "hit a little close to home". How does it feel to always be right?