The Incarnation, as viewed by Catholics, is a complex mystery that receives a great deal of attention from theologians throughout our Church’s history. Paragraph 460 in the Catechism of the Catholic Church states:
The Word became flesh to make us “partakers of the divine nature”: “For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God.” “For the Son of God became man so that we might become God.” “The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods.”
These quotes come from a time when the Church was embroiled in the Arian Heresy. St. Athanasius was a major player in attempting to argue for the divinity of Christ. He does this through is writing “On the Incarnation”.
Here is a link to that document.
Arius and his followers believed that Jesus was created by God the Father - and was thus not co-eternal with the Father and was also non con-substantial with the Father. However, Athanasius writes a document that discusses the experience of the Christian and how the teaching of Arius would invalidate the actual experience of the Christian. And, it was his arguments that carried the day at the council and thus defeated the Arian Heresy.
What is interesting about paragraph 460 in the context of this tread is that it has some verbiage that could be taken to support the LDS view of Christmas. God became man, that seems to line up. Then, there is this statement that he “might make men gods.” Whoa - what? Men becoming gods? That sounds very LDS like, doesn’t it?
However, difference between the Catholic understanding of paragraph 460 and the Incarnation, and the LDS teaching on Christmas is that Catholics believe that there was a point in time when humanity became “of the species of God” (that is my terminology - probably has some problems, but I’m trying to say that what St. Athanasius is talking about is what happened at the Incarnation to every human - not what happens later after a person dies and becomes a god themselves.) So, at Christmas, as Catholics, we celebrate that Jesus Christ, the second person of the Trinity, co-eternal with the Father, came down in unspeakable humility to take on human nature. At that moment, by virtue of this act, that self same human nature became elevated.
So, that is why, I think, that it is somewhat fair to say that the LDS view God becoming man as being just a “run of the mill” event. Before Jesus came down, heaven, he was already human. And so, the Christmas event was not disruptive whatsoever.
For the Catholic, the Incarnation is a tremendously disruptive part of human history. And, Mary, being the mother of Jesus, is uniquely honored for having the amazing grace to play an active participatory role in this amazing, happy disruption!