Numerous articles and blogs have noted the strong case to doubt Christmas' authentically "Christian" origins. Christ probably wasn't born on Dec. 25. The Puritans banned the holiday because it wasn't authentically Christian. And many of its rituals trace to the pagan celebration of the Winter Solstice or Saturnalia.
The modern understanding of Christmas is also significantly influenced by Charles Dickens' classic, "A Christmas Carol."
Charles Dickens, you see, was a Unitarian Christian. And "A Christmas Carol" preaches a decidedly (19th Century) Unitarian message on Christmas. To Unitarians, "Christianity" was all about good works and good will, NOT God's grace through Christ's atonement. And "A Christmas Carol" hardly ever mentions Jesus at all, but is about good works and good will.
Now, orthodox Christians likewise appreciate good works and good will. But that is secondary to God's grace through the shed blood of Jesus Christ -- God the Son Incarnate. And "A Christmas Carol" celebrates this message that the orthodox could consider at best secondary or incidental, not the central theme of the Christian religion.
That said, have a Merry Unitarian Christmas.