Christians decided to Christianise a Pagan holiday. Fact.
I'm a pagan. The pagan wheel of the year has a very definate mythology. At Yule 21 Dec, the God is born. This sparked a 7 day festival for the pagans, and 25th Dec is right in the middle of it. All the symbols of Christmas have their origins in the pagan festival.
However, if you are Christian, you can probably accept that the symbology itself isn't "evil" therefore celebrating it is alright if you celebrate it as the birth of Jesus.
I will celebrate it as the birth of Horus.
The whole pagan wheel of the year is mirrored in the Christian festivals. This is what Christians don't like to be told.
Sirona