I do like giving and receiving gifts, and I have no problem with all of us doing that in December, especially since it more or less coincides with Hanukkah. Naturally, we should, and I do, behave generously year round, but there is pleasant a kind of unity that comes from all doing it at once.
I also like to have a yearly reunion with family, friends, festivities, and food. It doesn't bother me that it revolves around a religious holiday or three.
The commercial nature of the season bothers me less these days, 8 years after selling my last TV, and since I no longer shop at malls. I heard my first Christmas music of the year on Christmas Eve at Cafe Passe, as I printed up a couple gifts in the gallery. I actually enjoyed whistling along to the old classics.
A lot of my fellow atheists go out of their way to post degrading things about religion in general, and Christanity in particular at this time of year. This bothers me a lot more than the store clerk saying "Merry Christmas", or God Bless". The clerk says those things with a kind heart and good intentions. The malevolently anti- Christian posts are just plain mean.
I am all about exposing perversion and hypocrisy in the church, and we all know it abounds. I am all about calling out those who would impose their religion on our rights and laws. I am all about disputing and debunking the pseudo-science promulgated by the Christian Right to the detriment of our education system.
Christmas is not the time to do it. This is the time when we should focus on the best of religion, not the worst. Say "Merry Christmas" back to the clerk. It won't hurt you.