I am one Atheist who is absolutely not involved in any kind of war on Christmas. I personally enjoy the holiday season very much and am very involved in spreading holiday joy!
Why do I love Christmas even though I consider myself a militant atheist? Most of all, I'd say it's because the glow of loving all humans is such a great feeling, and around the holiday season there seems to be so much of this. I do my part to get and give that glow at all times of the year. It seems like such a waste when people are only giving and loving during the holidays.
I don't really believe the war on Christmas exists. Even if it did, we would never be able to win the battle; it would be as futile as the war on drugs. I think certain religious groups, who somehow feel threatened by the idea that there may be other notions of the holidays or what they mean, have invented the war on Christmas as part of their great persecution myth.
So how does an atheist spread joy and cheer? It's not really different than anyone else, religious or not, but, as much as I love the holidays, everything I end up doing is pretty secular. I like to hand out holiday treat bags at work, but they always have reindeer or snowmen on them instead of Jesus. Second, I assist in planning the holiday party at work, and the gifts I bring to the party are always secular in nature. In our years of planning the holiday party, we have found that the least popular gifts are holiday-themed, and every year we ask people not to purchase them for the party because no one takes them! Sending out holiday cards to people who won't receive any that year is always a feel-good and simple thing to do. And it's fun to donate gifts to the Sharing Tree in our town. I would prefer that the Sharing Tree be run by a secular, rather than religious charity, but since the gifts go directly to people in need, it's a good cause, nevertheless. This year my family is going to be surprised that they are all getting donations in their honor to the Sharing Tree instead of presents. For example, my gift to my mom will be a winter jacket and a stuffed animal for a toddler.
I've thought of things that I could do to stand out as an atheist each Christmas season. I've often joked about including a card on my Sharing Tree gifts that says "Happy Holidays from a Loving Atheist!" I've looked at the upside-down Christmas trees and really considered buying one. I've thought of giving my friends and relatives memberships to atheist groups, even if they are not atheists. Although I think that's all very funny, it's really not the point. The idea is that other people need to be reminded that someone is thinking of them, and that this should happen year-round.
Would I be happy if all religious aspects were stripped from the holiday season? You bet! But I know this isn't going to happen, at least not anytime soon. As long as I'm alive, I'm going to make sure that others feel the same joy that I have been fortunate enough to feel every holiday, whether they're an atheist or not.