I had been on the path to becoming a Catholic for nearly twenty years. Coming from an Evangelical, Protestant background I had become an Anglican priest, learned to pray the rosary, understood and accepted the Catholic understanding of the Church, the sacraments and the priesthood. I spent a lot of time in Catholic Benedictine monasteries and attempted to follow the way of St Benedict. But I got stuck on the dogma of the Immaculate Conception of the Blessed Virgin Mary.
I understood the dogma, but didn’t know why the Catholics had to go and make it mandatory. As an Anglican I was comfortable with a certain amount of ambiguity–a certain open endedness to religion. Many things, I thought, were not clear in Scripture and therefore should be allowed to be held if people came to believe it, but that it should remain a “pious opinion.” In my worst moments I thought it was just another way for Catholics to exalt Mary more than necessary and that the whole things was not a “pious opinion” but an outright intentional deception.
UPDATE: For an in depth debate on this topic with an Evangelical. Go here for the chapter from my book Mary-A Catholic Evangelical Debate— on the Immaculate Conception.