I see nothing unreasonable about wishing someone, "Happy holidays," instead of possibly causing unnecessary offense by saying, "Merry Christmas," to someone who may not even believe in God. I think that the inclusive greeting shows greater concern for customers of all faiths.

I don't think that Christ is being taken out of Christmas by those who say, "Happy holidays," instead of "Merry Christmas." Christ is taken out of Christmas when we worry about trivialities and focus more on materialism than on "peace on earth, good will to men."

If this is something important enough to write a letter about, it's important enough to check your facts about. You are more likely to be taken seriously if you write a polite, well-informed letter.