Those who do not celebrate Christmas are extremely vocal in pushing the idea that Christmas is pagan. That the Roman Catholic Church back in the 3rd century, in an effort to Christianize the heathen, allowed them to bring their pagan practices into the church. Those who hold to this position would like everyone to believe that this is the one and only explanation for Christmas being celebrated on December 25 in the western world.
This article, written by Andrew Mc Gowan, Dean and President of the Berkeley Divinity school at Yale, disputes some of the assertions of those who call Christmas pagan. He also presents historical proofs indicating that Christmas was a product of Christians and not of the heathen.