I already answered.
Of course I'm celebrating Christmas. I'm not celebrating your Christmas. My family celebrated Christmas. My husband's family celebrated Christmas. I put up my Grandmother's nativity every year. I have an angel on the top of my tree as well as child copies of the nativity story. The entire Christmas season is special, to us. We have traditions and memories and doodads. We just don't go to church or recognize it as the birth of Christ. Plenty of professed Christians don't go to church so we're not that different. Shoot, I even wish people a Merry Christmas.
For many people, even agnostics and atheists, the holiday seasons are still meaningful to us based on tradition and we enjoy celebrating.
I don't get why this is hard.