Look it can google. There are over 1000 sites that discuss the origins of Christmas. Anyone can google a site to make their claim and defend it on a variety of points. The Pagan solistce ritual with the evergreen tree is just one.

The bigger point is none of it means a fricken thing if you understand that this world is ruled by freewill. That freewill allows man to do whatever he chooses. It has zero effect on the claim that one is Christian, the bible or god period. It is simply mans choice. The fact that it may be a sin is irrrelevent as well as the messiah came to forgive us for sin. It has about as much effect on the validity of biblical events or god as a box of Cheerios.