One of the big battles in the "culture war" is taking place over those who object to other's use of the inclusive greeting "Happy Holidays" over the use of "Merry Christmas." I find this rather silly. I also find those who whine about this "offense" rather ignorant over their own history.
December 25th, the day the Christian church celebrates Christmas, was chosen because of some very interesting parallels between the church's teachings concerning Jesus and the Indo/Persian god Mithra who was becoming very popular in the Greco-Roman world.
Mithra was believed to have been the son of God. According to Persian tradition, Ahura Mazda sent his son Mithra to defend humanity from evil and from the Adversary, Ahriman. Mithra was also believed to have been incarnated in human form, born from the immaculate conception of his Virgin Mother, Anahita, and around 200 BC had a last supper with his 12 apostles before he died for the sins of humanity. Mithra was born on December 25th as an offspring of the Sun.
Christianity has had a long history of co-opting local customs and cultures. One need only look at gospel music to find Christian rock, Christian rap, Christian soul, Christian country and so forth. So it should not surprise us that 2000 years ago, the church looked at a popular religion and decided to "convert" it to the church's use.
So, if Christians complain about the secular world "stealing" their holiday, they need only realize that "turnabout's fair play."