We need to reclaim Christmas. It's up to us. We can refuse to buy secular "holiday cards," refuse to let our children participate in "holiday pageants," at least the ones that don't include a preponderance of Christmas themes, beleaguer school administrators to muffle celebrations of other religions' holidays (got to keep that wall between church and state y'know), and in general refuse to patronize those establishments or traditions at odds with the Christian roots of the season.
CHRISTMAS IS A CHRISTIAN HOLIDAY! If the people who want to celebrate it refuse to acknowledge that, then they just want a day off work and a few cheap presents.
I refuse to buy anything but cards that mention Jesus. It's HIS birthday, nobody else's. I send them to my Jewish friends, african-american friends, etc.