Let's start here: Next Christmas season, whenever you are confronted with a "Happy Holidays" (especially at the point in time when both Ramadan and Chanakah (eek-sp?) have concluded), look the greeter straight in they eye and say, with a smile, Merry Christmas.
If a comment is made about it, look at them seriously (keep a straight face please) and ask if they would like you to recommend some sensitivity classes for them to help cope with their obvious problem of being intolerant of other people's religious views.
Do it over and over. Smile --- Merry Christmas. That's right, be subversive next December, wish someone a Merry Christmas.
I did that this year .. and added a God Bless You also
Have to say .. it sure felt good saying it .. and believe it not .. people smiled back at me and said Thank You