The thing is...when your parents were born, and when you were born, MOST baby boys were circumcised in the US. And although there were never any conclusive studies about medical benefits, and circumcision has always been done for religious, cosmetic, sexual, or hygienic (before it was possible to bathe daily) reasons, doctors DID (incorrectly) tell our parents it was 'healthier' or 'safer' to get it done.
Ask your parents why they think the baby should be circumcised. They might think he wants to look like everyone else, and as Romy said, now circumcision rates are about 50% and declining. They might think it's "cleaner", which was a reason for circumcision during periods long ago in history when it wasn't possible to bathe regularly. They might think it prevents infection or is safer, which is just downright a myth, and having them read any information on circumcision should inform them otherwise.