
I have no strong opinions on whether atheists should celebrate Christmas. It really isn't up to me, and it isn't something to which I've devoted much thought. If you enjoy it, derive some benefit from it, or simply want to participate in it, do so. You'll get no judgment here. Just because I see no reason to join in does not mean I'll think any less of you for doing so.
Some atheists seem to have developed a complex around their participation in Christmas. They try to justify their participation by claiming that Christmas has become thoroughly secularized in the U.S., promoting Winter Solstice, or even referring to themselves as "cultural Christians." I'm not sure if these efforts are directed at other atheists, Christians, or themselves, but I have my suspicions. In any case, they strike me as completely unnecessary.
If you are an atheist and you want to participate in Christmas, do so. I certainly don't need an explanation. I just wish that the same courtesy would be extended to those of us who have no interest in the holiday. Happy holidays.