I'm gonna outdo the War on Christmas.
You know how every year around this time the Religious Right starts up on those eeevilll liberals and how it's just wrong that they say Happy Holidays? Because, of course, retail salespeople should know exactly what holiday each of their customers celebrates and greet them appropriately. Or maybe it's because no holidays other than Christmas occur during December (well, other than Hannukah & Bodhi day, but those were made up to steal attention from Christmas amirite).
At any rate, I'm told that the only proper greeting right now is "Merry Christmas", because it's Christmastime, dammit! Only...it isn't. See, the Christmas season doesn't start until December 25th. The season leading up to the second-holiest Christian holiday of the year is Advent, dammit.
Ergo, anyone who makes a point of telling you Merry Christmas is not only an insufferable asshole, they're wrong. I hereby encourage all right-thinking Christians to stand up to the scourge of religious revisionism and combat the War on Advent.