A lot of good comments here.
As a pastor, I know the difficulty in the line we walk when we teach about such things. On the one hand, we need to teach the truth, and the hard facts about the origins of Christmas, yet on the other hand, we need to realize that some will still hold to some of the traditions, and we don't beat them up for it, or make them feel unwelcome. Not everyone is in the same place, in growth and maturity and discernment.
During the Resurrection time, I teach against Easter, and often do a version of Christ in the Passover, showing where Christ is seen clearly in the various Passover traditions, and as well, teaching where we got the Lord's Supper, as many, amazingly, don't realize it came from the Passover, from the Cup of Redemption, (His blood), and the afikomen, (His body), both aspects of the meal. I had a man in my church for many years-in fact, he was there before I was. He sat in this teaching many times, and sometimes, skiped out to go to take his kids to easter egg hunts at other churches. Well, he and his wife have moved a few years ago and this last year, they came out to visit and were at service when I did this Christ in the Passover, and he was amazed, and declared that he had never heard such things and he and his wife just gushed over how they loved it and how it opened their eyes up more than before. And yet, he had heard it before, but wasn't willing or ready, apparently, to receive it until then.
So with any of the traditional holidays-they tend to hold so many dear and precious family memories, it can be very difficult to hear the truth and give them up. So we need to be patient, give the truth, love them, and keep giving the truth, until they decide to take heed unto the doctrine.