Interesting debate. Here is what I think:
If you went to another country, and people were celebrating a particular holiday (whether or not connected to religious roots), and you saw the kids laughing and enjoying themselves, would you see it as a horrible thing? Would you ask for statistics on how many families actually celebrate that holiday? Or would you appreciate the tradition you got to witness?
Half of my family is Jewish (and we have immediate family in Israel). Half of my family is Christian. My dad claims to be an atheist. DSD claims to be agnostic at the moment (I think she is still figuring things out). Yet, no one would think to oppose a celebration that is prevalent in a given culture. The reality is, prevalent majority of Americans "do Santa" in one form or another, be it religious or just the stockings and reindeer kind of way.
I don't tell my sister to put away her menorah, and she complements my Christmas tree.
What I dislike about the whole thing is how taboo the whole subject is. Ya know what? If it wasn't for Christmas, there probably wouldn't the "the winter break". If it wasn't for Christmas, we probably wouldn't be saying to each other "Happy Holidays".
Santa is a great mythical figure and very few kids realize the religious roots behind him. Should we ban Superman? What if I don't like superman? Should we not discuss Greek Mythology at our school? That was based on very much religious grounds.
I teach, and I stay away from Santa, Christmas trees, and the whole bit, but I wish I didn't have to.