There are at least FIVE celebrations within a one-week period: Christmas, Yule/Solstice, Hannukah, Kwanzaa, and Humanlight. All of these are holidays taken seriously by their celebrants, even if only one is a "majority" holiday. I think it is nice to recognize that there are other people out there celebrating, too. I regard "Season's greetings" or "Have a good holiday" to those whom I know not to be Christians a matter of respect and good manners.

And yes, modern Christmas is a mix of mostly pagan and heavy duty corporate influenced symbols. If Christmas must be turned back into a Christian holiday again as it was "originally intended", then just go, "Good idea, get rid of all those horrible Pagan influences that corrupted it, like yule logs, lit-up evergreen trees, garland, mistletoe, giving wrapped gifts, etc"