I think those of us who feel strongly about this should politely let the managers of those stores who would rather eliminate Christmas from public utterance that we will be chosing to purchase our Christmas gifts from those stores that do not find us offensive.
IDEA: Go to one of these stores. Fill up a basket to the brim. Roll it to a register...and as soon as someone says "Happy Holidays" - abandon the basket and tell them that you are going to a store that still celebrates the real holy day: Christmas!