As we prepare for our celebration of Christmas, keep in mind that we are not observing “just another religious holiday,” taking its place alongside all the others. If Jesus Christ was born into this world in order to remake all of humanity through His sinless life, loving sacrifice of Himself on the cross, and powerful resurrection from the dead, then we ought to celebrate His birth. If He was not really what we Christians claim, then we ought not to celebrate His birth at all. If He was, then away with Ramadan, with Kwanzaa, or with any other celebration that cannot bow the knee to the Lord Jesus.
And so for us, there is not a genus called something like a “holiday season,” with our Christmas taking its place as just one example of that kind of thing. We are not allowed to place Christ alongside the idols at any time in the year, and if we were to do so at this time of year, we would be plainly contradicting the combined testimonies of the angels, the shepherds, Mary and Joseph, the wise men, and, in his own troubled way, Herod. If Jesus is the king, then that means that others are not.
The reason you hear about various skirmishes about Christmas trees in malls, or crèches in front of county courthouses, is because unbelief sees this principle far more clearly than the faithful usually do. Merry Christmas is always good, but take any clear opportunity you have to make it even more specific than that. “Have a blessed Advent” would be effective. So would “Have a good holy day.” Or “I hope your Nativity preparations are coming along?” And if anybody gets huffy, just laugh, all innocent-like.