I like what Matthew Yglesias says:
"It seems to me, really, that the whole Christmas spectacular would be much better if it just went unapologetically as 'Christmas.' If someone wants to know why I'm not in the 'Christmas spirit' the answer is easily enough: not Christian, don't celebrate the day, no spirit. The 'holiday season' has a weirdly insidious universalizing effect. Nobody's tricked into thinking it's anything other Christmas, but all of a sudden it's for all of us instead of merely the overwhelming majority of us. There's nothing wrong, really, with an overwhelming majority lording it over a small minority in such trivial ways as putting decorated conifers all over the place, but one might as well be clear on what's going on."