Well MY definition of an atheist is, "Belief that NO god/afterlife exists" Christmas, no matter what your opinion or how its perceived now (commercialism, greed, buying presents) is still celebrated because of the birth of Jesus. And yes I know that history shows that he was really born in spring/summer time frame. But I still see it as a religious holiday. I'm starting to think I'm the only one here that understands the true meaning? I mean, believe what you want to believe, its your freedom, it just gets me how SOME atheists love to try to make everyone believe what they believe, but yet go out and shun what they truly believe in to go with what the holiday signifies even if it means giving and receiving presents which has nothing to do with Jesus being born. Am I wrong to think this way? And yes I support peace on earth 
I think you misunderstand what an atheist is we are not organized (that would defeat the propose IMO). Yes, we do not believe in god but that’s were any commonality in beliefs end. The beauty about being an atheist is that you don’t have to conform to any standard religious belief we are free to celebrate what ever we chose. We can separate the religious dogma out of a holiday and make it our own; we celebrate however we see fit.
Maybe I was a bit long winded in my first reply to you question. As an atheist I celebrate Christmas either directly or indirectly for the following reasons;
1. In the US, Christmas is pretty much forced on all of us whether we believe in it or not (unless you hide in a cave for 3 months out of the year). This doesn’t bother me at all, as it is part of American culture, and I am an American.
2. Christmas is a good time to spend with family and friends. Believe it or not family and friends are important to atheists to.
3. The traditions of Christmas and time of year it’s celebrated are traditionally from the pagan celebration of winter solstice. So this celebration is not an exclusive christian thing.
4. I don’t see the problem with non-believers and believers getting together and celebrating a holiday. What’s the big deal? Besides it’s not very Christ like to exclude others based on religion or lack there of is it?
5. Christmas has very little to do with Christ anyway. Just ask corporate America how much they made off of it this year. They should probably change the name to Cashmas.
6. What should we do? Hide in our homes and not have fun with everyone else?
If all of us atheist party crashers really bother you then I would suggest that you pick a time in the spring and celebrate Christ’s birth in private by praying and by giving a gift to someone who really needs it or volunteering in your community.
