A Defense of "Mary, Did You Know"

Every year the song "Mary, Did You Know" catches flack because "Of course Mary knew who Jesus was!"
Setting aside the song's author and his beliefs, I think the song can be heard in a completely orthodox manner that serves to deepen our love of God.
This will be an emotional defense - not a robust logical defense. I make several assumptions and probably commit several logical fallacies. I simply offer this in the way I think the song was offered - according to every day usage of the modern tongue.