I see this play out every year. Someone complains that they can no longer say "Merry Christmas" because they fear someone else will be offended. How often does that really happen? I'm atheist and I'm never offended by good wishes, however phrased. If you want to say "Merry Christmas", then say it. It is possible you will meet a few idjits who get offended, but if they were raised with manners, they will return with kind words. If they return with insults, then you are the better person.