Christians might celebrate the birth of Jesus on December 25th, but that is not when He was actually born. Any true apologist, historian, or researcher following the details presented in Scripture will discover that Jesus was born during our September/October in Autumn, most likely on the Feast of Tabernacles. "The Word became flesh and tabernacled among us..." (John 1:14).
His birth, or the celebration thereof, was placed at different times of the year (January 6, March 25, April 10, May 29) before being fixed at December 25. Such early references to this date were based on superstitious beliefs and sloppy math. The commemoration of Jesus' birth on December 25th resulted from seasonal and mythological associations to pagan beliefs that are older than Christianity.
Why the Catholic Church chose to affix Jesus' birth to December 25th (apart from early superstitious beliefs and sloppy math) might be up for debate, but everything pertaining to the modern understanding of "Christmas" (originally called Christ Mass, one of two occasions where Mass is celebrated in the middle of the night when theoretically it should always be performed in broad daylight) is not. From Santa Claus and his flying reindeer to the evergreen tree, holly and ivy decorations, yule logs, wreaths, mistletoe, orb decorations, candles and lights, human-shaped cookies, singing from house to house, and gift giving, every single one of these traditions finds its roots and origins among pagan mythologies and legends. Everything about the American "Christmas" is associated with paganism, like it or not.
Early Christians may have suggested December 25th as Jesus' birthday due to superstitious beliefs and sloppy math, but what was the precise reason for the Catholic Church to deliberately affix it to this date? Why would you affix it to a time of clear pagan mythology and beliefs rather than to something Jewish? After all, all the Feasts find their fulfillment in Christ. To deny any sort of "Christianizing" of paganism is absolutely dishonest given the fact that the Catholic Church is notorious for such practices. In fact, they will defend the adoption of clearly pagan rituals, practices, and traditions as a means "to make it easier for people to join the Church."
If you want to celebrate Jesus' birth on December 25th, fine. Romans 14. But do not participate in all the other decorative nonsense associated with the holiday as it is absolutely abundantly clear that they are associated with pagan beliefs, rituals, practices, and traditions. "What partnership has righteousness with lawlessness? Or what fellowship has light with darkness? What accord has Christ with Belial?" (2 Corinthians 6:14-15). Why do you celebrate the birth of the Saviour in connection with obvious pagan elements? You are celebrating two things simultaneously, closely associating them all together, while attempting to deny the paganism attached to the one.