Indeed, starsareshining, the case put by your sister is just one of blinkered acceptance of some set of 'rules' of what is and is not acceptable.
I query whether religion itself should be foisted on anyone too young to make their own mind up... without going too deeply into the pros and cons of circumcision (I'm against, as I know of no widely accepted 'advantage' in it being done - medical reasons understandable but no other seems reasonable to me), it strikes me that religion does a lot of harm in raising tension in countries, up to the level of persecution and killings.
No child has the 'choice' of being born of rich or poor, in an industrial country or on a hillside in the tropics, or their religion, because the first two aspects are pure chance, the religious (and traditional/ cultural) aspects are dictated by their parents, including (for some) marriage, circumcision, and other things.
While I am tolerant of others having [religious] beliefs, or none, I am less tolerant of any group trying to persuade others to follow their beliefs, whether as adults 'selling' their thinking to others, or as parents 'forcing' their children to accept some set of rules as the only (or 'best') option (sometimes to the exclusion or hatred of any others).
BootyMum, I think PussinJC was just wanting to correct spelling, without any 'hidden agenda' let alone being pro-circumcision, but if you try searching, best have the correct spelling, eh?