Perhaps the greatest of many great gifts to the Church from my favorite Pope, Bl. Pius IX:
Let all the children of the Catholic Church, who are so very dear to us, hear these words of ours. With a still more ardent zeal for piety, religion and love, let them continue to venerate, invoke and pray to the most Blessed Virgin Mary, Mother of God, conceived without original sin. Let them fly with utter confidence to this most sweet Mother of mercy and grace in all dangers, difficulties, needs, doubts and fears. Under her guidance, under her patronage, under her kindness and protection, nothing is to be feared; nothing is hopeless. Because, while bearing toward us a truly motherly affection and having in her care the work of our salvation, she is solicitous about the whole human race. And since she has been appointed by God to be the Queen of heaven and earth, and is exalted above all the choirs of angels and saints, and even stands at the right hand of her only-begotten Son, Jesus Christ our Lord, she presents our petitions in a most efficacious manner. What she asks, she obtains. Her pleas can never be unheard.
Here are two very no-nonsense little commentaries on the dogma, by two world-famous Catholic preachers who were very good at talking to Protestants.
A Protestant is apt to say: "Oh, I really never, never can accept such a doctrine from the hands of the Church, and I had a thousand thousand times rather determine that the Church spoke falsely, than that so terrible a doctrine was true." Now, my good man, WHY? Do not go off in such a wonderful agitation, like a horse shying at he does not know what. Consider what I have said. It is, after all, certainly irrational? is it certainly against Scripture? is it certainly against the primitive Fathers? is it certainly idolatrous? I cannot help smiling as I put the questions. Rather, may not something be said for it from reason, from piety, from antiquity, from the inspired test? You may see no reason at all to believe the voice of the Church; you may not yet have attained to faith in it--but what on earth this doctrine has to do with shaking your faith in her, if you have faith, or in sending you to the right-about if you are beginning to think she may be from God, is more than my mind can comprehend. Many, many doctrines are far harder than the Immaculate Conception. The doctrine of Original Sin is indefinitely harder. Mary just has not had this difficulty. It is no difficulty to believe that a soul is united to the flesh without original sin; the great mystery is that any, that millions on millions, are born with it. Our teaching about Mary has just one difficulty less than our teaching about the state of mankind generally.
I say it distinctly--there may be many excuses at the last day, good and bad, for not being Catholics; one I cannot conceive: "O Lord, the doctrine of the Immaculate Conception was so derogatory to Thy Grace, so inconsistent with Thy Passion, so at variance with Thy word in Genesis and the Apocalypse, so unlike the teaching of Thy first Saints and Martyrs, as to give me a right to reject it at all risks, and Thy Church for teaching it. It is a doctrine as to which my private judgment is fully justified in opposing the Church's judgment. And this is my plea for living and dying a Protestant."
--John Henry Cardinal Newman
Just suppose that you could have pre-existed your own mother, in much the same way that an artist pre-exists his painting. Furthermore, suppose that you had the infinite power to make your mother anything that you pleased, just as a great artist like Raphael has the power of realizing his artistic ideas. Suppose you had this double power, what kind of mother would you have made for yourself? Would you have made her of such a type that would make you blush because of her unwomanly and un-mother-like actions? Would you have made her exteriorly and interiorly of such a character as to make you ashamed or her, or would you have made her, so far as human beauty goes; the most beautiful woman in the world; and so far as beauty of the soul goes, one who would radiate every virtue, every manner of kindness and charity and loveliness; one who by the purity of her life and her mind and her heart would be an inspiration not only to you but even to your fellow men, so that all would look up to her as the very incarnation of what is best in motherhood?
Now if you who are an imperfect being and who have not the most delicate conception of all that is fine in life would have wished for the loveliest of mothers, do you think that our Blessed Lord, who not only pre-existed His own mother but who had an infinite power to make her just what He chose, would in virtue of all the infinite delicacy of His spirit make her any less pure and loving and beautiful than you would have made your own mother? If you who hate selfishness would have made her selfless and you who hate ugliness would have made her beautiful, do you not think that the Son of God, who hates sin, would have made His own mother sinless and He who hates moral ugliness would have made her immaculately beautiful?