Yes I agree the woman's argument was correct and it is worrying that Circumcision is allowed if both parents agree its no different to Female Circumcision which is illegal that is practiced for religious reasons.The father's argument was very poor the child shouldn't be circumcised in accordance with his "Muslim practice and religious beliefs" not only is he wrong here because of the fact that he said his it is not known yet whether his children will follow his religious beliefs parents shouldn't get to choose the religion of their children they should have free will but also for the fact he mentioned Muslim practice without any justification for why God would want such circumcision religious texts/documents are not evidence(like the Sunnah).
Most people get religion the wrong way round you need to decide what you believe and why and then choose your religion based on your religious beliefs and arguments the other way round is caused by indoctrination by society, faith schools and parents.