Merry Christm....I mean, Happy Holidays! Er... Oh wait, phew...we're past all that pretending to ignore Christmas for another year (although technically, this is just the second day of Christmas...).
What is it about "Happy Holidays" and "Merry Christmas" that gets people so worked up? Theoretically they are both joyful greetings, right? "Happy holidays" is hardly a new invention. Surely in the past (and even sometimes now) it was an abbreviation of "Merry Christmas and Happy New Year," with the intent clear to both parties. So, there's certainly nothing *inherently* wrong with the greeting of "Happy Holidays." That said, it does seem in more recent times to be used as the PC all-inclusive winter greeting....intending not to say "Merry Christmas and Happy New Year" but "Happy/Merry [insert your winter celebration here]"
As to the idea that we shouldn't say "Merry Christmas" in order not to offend ...someone... Well, look around at society's celebration of Christmas. Is it a religious holiday? Granted, because it is celebrating the birth of Christ, it couldn't ever be fully secular....but for all intents and purposes, Christmas is a secular American holiday. Keep an ear out for the jingling of reindeer bells, while you set out your cookies and milk for St. Nick (Oh, pardon me, I mean Santa Claus)...and if you've been good enough, you'll get a boatload of new crap. Exactly what makes that something to offend someone else of another (or no) religion? Plenty of non-religious people celebrate Christmas, and do note that they're celebrating Christmas, and not some other "winter holiday"...because it's *Christmas* which has become the generic, secular holiday.
Given that, it's hard to make an argument that you shouldn't be able to say Merry Christmas for fear of offending someone. Do you hold off on greeting someone with "Happy Thanksgiving" before checking to find out first if that person in fact even celebrates it?
Frankly, isn't "Happy Holidays" just as "offensive" as "Merry Christmas"? Holiday, after all, means Holy Day.
If you just can't decide which greeting to choose, feel free to say Happy Birthday Adam! My baby guy's birthday is Christmas Day.