Today's feast has got to be the most gruesome commemoration in the entire liturgical year, based on the most unsettling story in the New Testament. What's it doing coming on the "Fourth Day of Christmas"?
I read a great remark about this very thing: the author pointed out that our cultural conception of Christmas with tinsel and fluffy-winged angels isn't all that Christian at all. What today's in-your-face feast tells us is that God's Son came to an earth in need of redemption. A sinful place. A place that can get ugly real fast. Medieval representations of Christmas were unsparing in their depiction of the slaughter of the innocents, whose number was assumed to be astronomical.
Herod's tiny victims weren't the first babies to be sacrificed to a local ruler's ambition (think Pharoah and baby Moses), and God knows they weren't the last. The Holy Innocents were, in a way, a prophecy that "a sword would pierce the heart" of anyone in league with Christ. Today's Gospel warns us to take that Babe in a manger very seriously.