What about non-Christians?
Exactly, 'Merry Christmas' to all. Seriously though, it's all about being kind and patient with people. Because the Christians represent the largest number of a single religious order on this planet (who knows for how long), plus it's that time of year hence the association with good intentions has to be practiced more now than during any other time.
Without trying to sound too much like some failed hallmark greeting card, Christmas hasn't ever been linked to any Early Christian scriptures. Hence the mass-marketing of the birth of Christ was excellently handled by your country the US. So for me, the idea of Merry Christmas (without Santa Claus) has always meant the celebration on the birth of the Christian deity's son. I know in your country now (the US) there are lots of secular movements trying to grab the limelight for themselves which is understandable, but it's still that time of year that this current festivity (progressed into mainstream from 400AD) has been practiced. So what ever religious affiliation you belong to, no one is restricting your own belief system in any way, hence that same reciprocation should be practiced universally.
So instead of trying to cripple, bare ill will and deride others around you, showing compassion shouldn't be seen as some sort of disease that needs to be stamped out immediately, like here on Geekhack. If you can't possibly be nice to anyone around you........then try and give a little compassion to the key-cap organizers, moderators and sellers here on Geekhack. It won't cost you a dime and you can always gear up for more 'nastiness' in 2013.
After all what's the rush, you can always get what you want later in 2013.