The nature and purpose of Original Sin

Original Sin is not just the acknowledgement that nobody's perfect, but a means of allowing the priesthood to put a foot into the door of the subject of Christian monarchs. The narrative is that infant baptism is necessary to avoid the infant spending the rest of its afterlife in purgatory if it died in infancy.  

Judaism uses infant circumcision as a marker of Jewishness, therefore baptism is used as a marker of Christianity for the infant. Let us not forget that those who proposed credal baptism were systematically burned at the stake for daring to suggest that the subject of the absolute monarch might have a different opinion on whether Jesus was in fact the co-equal of the God of Israel who is also Allah.