When you boil it down Christmas is only about the celebration of the birth of Christ, not about toys or trees or twinkly little lights. Just Jesus. Christians should instead be insisting everyone call it a "Pious Christmas" or a "Faithful Christmas" but that's not as marketable as "Merry Christmas".
The "happy" part of "Happy Holidays", on the other hand, is mostly borrowed from the pagans. You know, the feasting, decorating, gift-giving stuff.
As for Fox News' Megyn Kelly, who so famously opined that both Santa and Jesus were not only real but possessed of a radiant skin tone similar to her own pinkish hue, let me just say that while I have my doubts about the historical realitiy of those two characters I definitely know that Hitler and Stalin were both white, too. So if you're gonna claim the good white people, Megan, you little racist twat, you gotta take 'em all.