I celebrate Christmas, many do not. I try my derndest to be sensitive to what someone's religion might be. If in doubt, and I often am, I either ask what they celebrate, and go from there, or, wish them a happy holiday.

To me, I wouldn't wish someone a happy birthday if it weren't their birthday anymore than I would wish everyone a Merry Christmas, if they don't celebrate that holiday.

If I want my greeting to be sincere, it should reflect the beliefs of the person upon whom I am bestowing it on, right? Not mine...otherwise, you would wish yourself a Merry Christmas. LOL.