I don't see any value in holidays myself, but at least I won't be negative about it towards people who do. I recently sent out Christmas cards to a couple dozen relatives...because I am fairly sure that THEY celebrate it. Not that big a deal. My message inside was basically the same, though I tried to change up the wording from card to card. "May the season bring you love, hope, joy, and peace." Nothing specific said about Christmas, and still a positive message.