I agree with (at least) the first line of Copernicus' post.
I appreciate it when people wish me well, whether it's "Happy holidays" or "Peace be upon you". I may prefer a person would not bring up the name of his favorite pagan deity, but you don't look a gift horse in the mouth. (There may never have been a better use for that particular expression.) It seems to be like complaining about the color of the new car one's great uncle might give one for graduation. The graduate just got a new car, who cares if it's too bright in color?
I oppose government promoting one particular religion above another, so I oppose requiring students recite the Pledge of Allegiance in school; but I also oppose the use of the government to forbid a private business or citizen from promoting his own personal religious beliefs. So it's fine with me if a store has a policy of having "greeters" and cashiers use "Happy Holidays" rather than "Merry Pagan god/man-birthday!" (or whatever), or even vice versa, a store requiring its employees to wish customers a "Merry Christmas". If the employee doesn't want to do it, he can go find employment elsewhere, and the employer can find somebody who will follow instructions. It's also okay with me if the pagans (or whoever) refuse to shop in such a store. But they should not be able to have a "law" passed that would keep stores from allowing their employees from promoting christmas while acting as agents of the store. You want to promote christmas and the store's management opposes it, then do it on your own time. (Interestingly, the military approves of military personnel attending religious services in the house of worship of the military member's choice - even in uniform.)