In twi, it was fine to celebrate the Birth of Jesus- so long as you did so on September 11th (and looked down on people who celebrated any other day.)
Celebrate Christmas? lcm used to claim that Christmas (named after the Christ Mass people attended) was named after the MASSACRE of the innocents by Herod. (So, the holiday of Candlemas would have commemorated the massacre of a lot of candles, etc.) Yes, when I was in, I knew he was wrong. But, could not celebrate Christmas or Advent.
Mind you, in twi, it was totally fine to celebrate a Household Holiday (Ho-Ho) on December 25th, with a decorated tree, presents, carols, and so on. You were totally not supposed to celebrate Christmas. Seriously, I'm NOT making ANY of that up!