I asked the question five years ago. I didn't really get an answer then and I haven't really got an answer since.
The closest I've come to getting it can basically be summed up in one sentence: «It belongs to everyone».
As if it’s a good thing.
It is really true. You get most disappointed by people you think should know better. Atheists celebrating Christmas are nothing but apologists for the greed and fanaticism of capitalism and Christianity.
It’s very important to expose events like Christmas for what they truly are and not give in, and join in on the deception, and thereby supporting it.
Whether you call it Christmas or Xmas is totally irrelevant.If you want to celebrate any official or semi-official day these days or nights celebrate the Winter Solstice and do so at December 21.