Christ mass is Christian in name only like most "Christians" today. Christ mass is a Roman Catholic holy day that a true born again believer has no business celebrating. Saying you are worshipping God but doing it in a way that He never prescribed nor put His approval on is not truly worshipping God, but self. We are told to come out from among them and be years separate, and to not love the world or the things of the world. The season represents worldliness, covetousness, bondage, idolatry, and rebellion. Those all seem like good reasons to "abstain from all appearance of evil", no?
It has been said that most people don't even know what they are worshipping at Christmas time. Amen. If they are celebrating the way the world does then they may not know it, but they are worshipping idols. Just because you clean a pig up and put a dress on it, doesn't change the fact that it's a pig. Christ mass is just dressed up paganism, plain and simple. You don't have liberty to worship God any old way you choose. God is looking for people to worship Him in spirit AND in truth. And the truth is, Christianized paganism is still pagainism.
Since the holiday was started by the pagan Catholics, it's no wonder they didn't change it much from its Baal worshipping roots as Catholicism is just repackaged Baal worship at its core. Sure it's more palatable than Satanism but that also makes it more dangerous as the subtlety ends up deceiving more people than blatant Satanism EVER could.