The very name Christmas comes from Catholicism (Christ's Mass). There are many people who eschew all things Catholic but seem to have no problem celebrating Christ's Mass. The date December 25 is the day of the winter solstice according to the Julian calendar used by the Romans. It was the day of the sun's rebirth.
So we see, December 25 has both Catholic and pagan origins. Many will argue that they are okay celebrating Christ's Mass because they simply ignore the Catholic and pagan elements and remember the birth of our Lord. But how does one ignore the Catholic and pagan elements when the very date and name reflect them?
I would suggest if Christians can't help themselves from observing our Lord's birthday, a new date and name should be chosen that doesn't reflect Catholicism and paganism; something that is separate and distinct from the world.
I don't know about God, but I would be happy knowing people, who love me, celebrate my birth and life, regardless of when they do it or why they chose that date. But eh, that's just me, and you are free to celebrate in any way at any time you choose...Or not.