The real "reason for the season" is the natural astronomical holiday. We all like to honor the shortest day of the year with lights, food, gifts, fun, music, and family gatherings, as it signals the return of the sun for another year. While everything in the upper northern hemisphere is dark and colorless, the evergreen signifies hope for a returning spring. None of this is supernatural. It has nothing to do with the birth of a god.
In America, Christians are welcome to celebrate whatever they want. We are happy to share the season with them. They just can't use the government to privilege their party over everyone else's.
MORE: http://www.washingtonpost.com/blogs/guest-voices/post/former-minister-we-atheists-love-this-time-of-year-like-everyone-else/2012/12/05/1eaac96a-3f0d-11e2-bca3-aadc9b7e29c5_blog.html