You know what the real problem is? People don't understand that the concept of decorating a Christmas tree is, in fact, a Pagan tradition which some way or the other has been associated with Christianity.
http://www.religioustolerance.org/xmas_tree.htm
If they had put up a menorah then someone else would have undoubtedly claimed that they're religious beliefs were being left out or that they were offended by the showing of religious artifacts. Really. People can get angry over the most trivial of details. The way I see it, if you're offended the close your eyes, take a deep breath and move on. It's not the airport's duty to try to appease everyone.