The dispute makes no objective sense, of course. "Holiday" means "holy day." Holy for what reason? For the reason that Christ was born: absent which occasion the stores wouldn't be bidding you, come max out your credit cards. You'd think we could have sailed on another 40 or 50 years serene in our Christian pan-denominationalism.
On the other hand ...
Even pan-denominationalism isn't a good fit in a world wary of spiritual entanglements. Free-market capitalism, God bless it (there I go again!) not only maximizes prosperity but encourages the personal autonomy and fragmentation that have become our moral hallmarks. In other words, our popular creed, instead of "Jesus Saves!" seems to be "Lemme Alone, Hear?"
High expectations for human performance really don't inform the new creed, which, unlike traditional Christianity, isn't long on moral reasoning, with its encouragements, restraints and, indeed, prohibitions.
To the degree you suggest to someone else how life should rightly be lived, you invite the angry retort or the indifferent stare. Lemme alone! Outta my face!
But the nature of Christianity -- the creed of Christmas -- is about unpleasant realities like human deficiency and humbling ones like redemption: all in accordance with divine directives.
To be wished a Merry Christmas is to be wished a closer walk, a nearer relationship, with the God whose only begotten Son, as the story goes, came to earth at this season. The manger thing, you know -- angels, shepherds, wise men. Oh, so entangling! As it was meant to be.
Oh, and, by the way, Merry Christmas.