Why don't Jehovah's Witnesses celebrate Christmas? It is likely that Jesus celebrated the Jewish holidays when he was in physical form.
Jehovah's Witnesses believe that the early Christians did not celebrate the birth of Christ, nor did they care when he was born. They say that early Christians didn't even know when Jesus was born. Also they say that celebrating birthdays does not make Jehovah happy.
Jehovah's Witnesses view Christmas as a birthday and they believe that God doesn't want us to celebrate birthdays. See Why Don't Jehovah's Witnesses Celebrate Birthdays?
The Watchtower tells Jehovah's Witnesses that celebrating Christmas is wrong, and faithful Jehovah's Witnesses trust the Governing Body. The Watchtower teaches Jehovah's Witnesses that 'the slave' must be trusted completely. And the Watchtower says they are God's slave that Jesus spoke about in Matthew 24: 45-51. Learn more about the Faithful and Discreet Slave
Therefore Jehovah's Witnesses believe they are making Jehovah God happy by not celebrating Christmas. They believe that Jehovah says they can't celebrate Christmas.
The truth is that Jehovah has said nothing about Christmas in the Bible. Since the Bible is silent about celebrating Christmas, one would think that the organization would not interfere with a Christian's right to put God and the Bible first. However this is not the case.
Regardless of whether an individual's conscience would allow them to celebrate Christmas or not, celebrating the holidays is forbidden within the organization. Rebellion against the leadership of the organization can lead to disfellowshipping, disassociation, and shunning.