I guess if you had to label me anything (though why you'd want to is beyond me), I'm an atheist. But I still love Christmas. That's because it's such a good story, with virgin and manger and star and wise men and shepherds and angels proclaiming peace on Earth. And stories are what we use to make sense of our lives -- as long as we realize that they are stories. If there were holidays celebrating the courtship of Elizabeth and Darcy, or Ahab's pursuit of the white whale, or Frodo's taking the Ring to Mount Doom, I'd celebrate them too.
Stories are always true, because they come from the rich imagining of the human mind. They only become false when people use them to further their own ends, finding ways to warp and distort them into creeds and causes and religions and ideologies. When an ugly old man in the Vatican uses a Christmas address to proclaim his hatred of gay people, or when a TV network promotes closed-mindedness by claiming that those who want to include all believers and non-believers in their celebration of a holiday are somehow waging war on Christmas, then the stories become false.
So whatever you believe, peace be unto you.