I had just the opposite experience last Christmas. In almost every instance, my wish of Merry Christmas to store clerks, bank tellers, phone callers, and, yes, at work, among other places, yielded a muttered Happy Holidays or Season's Greetings.
What surprised me most was that many of these same people were members of the Church choir I play along with, or members of my church, and the generic greetings were issued at the Church. I live in a small predominantly Catholic/Christian town where many people know one another. I've been greeted with Happy Holidays and Happy Chanukah at work, and I respond in kind. Not unusual at all and celebrates with others the secular aspects of the season and the faiths of others.
But in church by other church members, a 'Happy Holidays' is a nice enough greeting but one that falls flat, especially at the Christmas Eve vigil (that one really surprised me). I do believe that is what he is trying to save.
I'm not a Christian in the believing sense of the word, but I was raised in Christian culture. I don't think it would be too much to ask for businesses that profit from it to acknowedge "the reason for the season", as they say. Heck, even those of us who don't particularly believe can appreciate the message of Christianity and share the sentiment at Christmas. Even the faithful Muslims I work with are more than willing to toss out a hearty "Merry Christmas" at that time of year.
Holiday = Holy day. Holy = separate, apart, different.