I'm with you Grey. haha.

I've been doing this. Everyone that says "Happy Holidays" to me, I reply back with a "Merry Christmas".

I still think that the secular holiday should be refferred to as Xmas, though that pronounciation apparently isn't a modern abbreviation. It's not like christians now think Mary gave birth to Santa at the North Pole on Christmas day or anything, so you can't say that it's not a religious holiday anymore, whether a majority of people celebrate it for non-religious reasons or not.
And yes, I know Jesus, biblically, wouldn't have been born on christmas either, get over it. Christians needed the excuse to hijack a pagan holiday instead of starting another crusade, and paying homage to when Jesus was born works pretty well.

And actually, it's not overreacting, my fiance is dealing with it at work already, where most people are defaulting to a generic "Happy Holidays" even if they do celebrate Christmas. Admittedly, it's not as bad as a couple cases you heard some 5 years ago or thereabouts, when people were really getting snotty about it.

Does it really just ruin your entire day that someone says "Happy Holidays" instead of "Merry Christmas?" You say your fiance is dealing with it at work almost as if it's some kind of nationwide plague or fad. It's really the most pointless thing imaginable to get angry about, and it wouldn't be so bad except for the fact that most of the people who complain about it are angry old conservatives (Bill O'Reilly, Pat Robertson, etc.).