Nissenbaum's book reminds us that not until the fourth century did the Church officially decree Dec. 25 as the date for Christmas, because it roughly coincided with the winter solstice, already long observed with a pagan festival.
Leaping ahead to the United States of the 1840s, the holiday had begun to resemble the Christmas we observe today, with the popular poem first published two decades earlier, "'Twas the Night Before Christmas," serving as an influential guidepost. And already — with images of Santa Claus even then being used in advertisements aimed at children — people were decrying the holiday's commercialization.
In short, Christmas has always been in flux and at odds with itself.
Nissenbaum (who during a recent phone interview noted that he was making no references to O'Reilly, whose show he said he's never seen) reflected on the proposition that a Christmas tree is cultural and secular, and therefore shouldn't offend non-Christians.
"That makes real sense only if the people making that argument don't think of Christmas as a religious holiday," he said. "The moment that you see Christmas as a Christian holiday, then something that bears the name 'Christmas' has got to have a religious significance." In other words: You can't have it both ways.
But you can sure try. When it comes to war coverage, O'Reilly spent less than 14 minutes on the wars in Iraq and Afghanistan last December, while devoting roughly 42 minutes to the War on Christmas, according to liberal watchdog group Media Matters for America.
As an "O'Reilly Factor" franchise, the War on Christmas is just the latest chapter in the holiday's contentious history. It makes Christmas a political wedge issue. It's a celebration that, under the pretense of peace and goodwill, is ripe for fighting about on his show.
"Beyond all the controversy lies a much bigger secular progressive agenda," insists O'Reilly, rallying his troops.
Call it what you like, Christmas waged like that is just an annual observance of Us vs. Them.
EDITOR'S NOTE — Frazier Moore is a national television columnist for The Associated Press. He can be reached at fmoore(at)ap.org and at http://www.twitter.com/tvfrazier