A lot of my friends, especially those who don't identify as Christians, prefer to say "Happy Holidays" rather than "Merry Christmas", and I get that. In fact, I not only get it, I'm grateful for it. "Happy Holidays" serves a number important functions: it reminds us that there are more holidays in our community than just the Christian ones, and therefore undermines attempts at Christian cultural hegemony; it socially releases people who are not Christian from identifying with a Christian holiday in their greetings; and it doesn't assume that this Christian holiday is the primary reference point for the person you're with.
All of this is deeply respectful of the person in front of you, and completely appropriate for a pluralistic society like ours. I also think it's deeply Christian. As a Christian, I believe we shouldn't use cultural power to coerce people into our spiritual frame of reference, however deeply we may believe in it. (BTW - part of why I believe that is the posture of the God in the Christian Christmas.)
But that's not the only reason I'm grateful for "Happy Holidays." I'm grateful because it reminds us that Christmas is not just a cultural holiday shared by all, the one so often defined by shopping, jingles, lights and trees. That's "The Holidays." "The Holidays" is the new cultural Christmas, and I love that because it allows Christmas to be what it has always actually been: this very strange and specifically Christian day celebrating when God became Human.
During Christmas, we don't celebrate consumption, and we don't worship family, as meaningful as that time together can be. Instead, Christians celebrate that the God of the universe broke into history as a dark-skinned, Palestinian Jew, conceived by a low-income, unwed mother in a land under occupation. God's Son literally identified himself with the economically vulnerable, the socially overlooked, and politically oppressed. Christmas, unlike The Holidays, doesn't just offer us expensive distractions from the pain of the world, but a divine way of engaging more deeply in it with God as our radically committed, ever-present companion on the journey. Christmas is about so much more than nice warm memories. It's about God's salvific solidarity with the world he loves.
That's why even though I really enjoy The Holidays, I deeply love Christmas.