This shouldn’t be hard. If you’re an atheist, and you greet somebody who you know is a practicing Christian, decorum would suggest that you say “merry Christmas.” If you’re a Christian, and you know you’re greeting an atheist (or a non-Christian generally), decorum would suggest “happy holidays.”
Why? Because any friendly greeting is necessarily deferential to Otherness. It’s not about you. It’s an acknowledgment that, where we differ on matters religious, we nevertheless recognize and tolerate differences among us.
So whence the so-called war on Christmas? It’s about the resentment that those on the American right feel at the very notions of difference and tolerance. They seek central pride of place to their religion as “normal” and don’t want to acknowledge the existence of diversity in their communities. They thus make the greeting about them and their happiness, not you and your happiness. It’s a form of selfishness; a lack of love and charity–all, ironically, in the name of Jesus.
It’s really that simple.
But what if you’re addressing, not an individual, but a mixed group of Christians and non-Christians? Again, this shouldn’t be hard. “Happy holidays” covers everyone. Or, as an alternative, you might say, “Merry Christmas to those who are Christians, and happy holidays to everyone else.” It’s about respect.
The alternative is religious conflict, which is captured magnificently in these lines from James Fenton’s great poem, “Jerusalem”:
It is superb in the air.
Suffering is everywhere
And each man wears his suffering like a skin.
My history is proud.
Mine is not allowed.
This is the cistern where all wars begin,
The laughter from the armoured car.
This is the man who won’t believe you’re what you are.