Be my guest! (Not that you owe it to me, just like you don't owe Orin a beer.)
I don't celebrate Christmas as a religious holiday, but so what? If you wish me a Merry Christmas, is it really reasonable for me to interpret this as a wish that I have a deep relationship with Jesus on this day? I rather doubt it -- "Merry [anything]" isn't much of a call for serious religious action or introspection. Nor is it an assumption that I'm religiously Christian. Everyone, certainly including religious Christians, knows that tens of millions of Americans, including those raised nominally Christian, don't celebrate it as a religious holiday.
Perhaps saying "Merry Christmas" is a reflection of the fact that most of America is culturally Christian, in the sense that it celebrates traditionally religious holidays. But that is indeed a fact. Saying "Happy Holidays" won't hide it, and saying "Merry Christmas" hardly rubs it in anyone's face (especially given the Santas and other paraphernalia you're in any event likely to see all around).
Moreover, Christmas is a day off for people without regard to religion (except for those who work in businesses that require them to work that day, there probably also largely without regard to religion, except for the comparatively devout). Chances are that your Jewish colleagues are doing something fun for Christmas. I am, and I had done that each year even before I married my culturally Christian wife. Why shouldn't we be merry on these occasions?
So if you tell me "Merry Christmas," good for you. If you tell me "Happy Holidays," I confess I'll get a bit annoyed because of its generic air, but I'll just assume that you're trying to play it safe -- often a very good strategy in social relations. Plus why be churlish about someone wishing you a happy anything? If you tell me "Happy Hanukkah," I'll start racking my brains about when Hanukkah actually is this year; I never have any idea. If you tell me "Happy Diwali," I'll assume that this is a good thing in your life, and I'll appreciate the good wishes. (If neither you nor I are Hindu, then I might wonder what you mean by that.) If you tell me "Happy New Year," my favorite greeting, I'll be extra pleased, but that's just a matter of taste.
So, Merry Christmas, everyone -- yeah, all you Russian Orthodox, too, I know all about your old calendar, but you're in a Gregorian country now, buddy. And best wishes for a happy new year!