I agree with everything you say, MREG2.
But adults should also be able to reason that if I wish them Happy Holidays, I'm not trying to take Christ out of Christmas. I don't want to have to worry that some group is going to boycott my business because I choose to say Happy Holidays to my clients this time of the year. My contact with them is only over the phone, I have no idea if they celebrate Christmas or not. But I do, and in the spirit of the season, I want to send them good wishes in an all inclusive way.