So in keeping with Political Correctness :) Speaking only for myself of course, Merry Christmas has always worked for me as it is a part of who I am to those who wish the same. To all others it's bah humbug because I want to be respectful to those who wish the same. 

Merry Christmas!.....to those who wish the same.
misery bah humbug!....to those who wish the same.

Good now everybody is covered and I'm glad no one can say they were left out.