If you drop me a note to let me know that it matters to you, I will very happily and honestly send you a deeply religious Christmas card. With Jesus and the nativity and a very serious Christian message. I will neither sneer at you, or make the slightest sarcastic remark to myself when I send it. I can honestly do this, and I will in fact feel very good about myself in doing so.
I believe very strongly in religion, and faith, and I would never insult someone for having faith. I honestly and truly believe that true and deep faith is a beautiful thing, and I wish that many more people had it.
Because I respect your faith, and I know that you respect mine, I look forward to receiving a card from you this holiday honoring my faith. And I know that your card will show the same respect and consideration for my religious beliefs and celebrated events, as I have put in my card to you. The birth of the Sun God and the beginning of the waxing cycle of the year is a deeply moving time for me.
Don't forget that we celebrate on the 21st of the month. I'm sure that you can find an appropriate card at your local Hallmark...