Are atheists really responsible for taking the "Christ" out of "Christmas?"?

This time of year I start hearing the “put Christ back in Christmas” discussion. It always seems to have a finger pointed right at the atheists, but I’m curious to know why. I don’t ever remember hearing about mass boycotts of stores that say “Merry Christmas” or groups of atheists protesting in front of a store with a Christmas tree in the window. Did I miss that? Or did it never happen?
I always felt like “Happy Holidays” was about marketing. About being inclusive. You don’t have to celebrate Christmas to shop at our store, buy your loved ones their Hanukkah gifts, festivus presents, solstice gifts, giftmas presents, hell.. a New Years present, we don’t care what you celebrate, just give us your money!

Is that not what it is really about? Were atheists really behind this in the first place?