I'm from a Christian background, and my husband's is Muslim. When someone wished me a "Iyi Bayramlar!" when we lived in Turkey, I didn't get offended. I took it in the spirit in which the person had said it, which was at the "Have a nice day!" level of social pleasantries.
So, I put it to you in the comments: is it really offensive when people wish us well from within their own cultural framework? And it is really offensive for people to wish us "Happy Holidays!"--even if they don't tailor it to our specific beliefs? They're wishing us GOOD stuff, people! They aren't trying to offend us!
Just so we can all be clear on the difference, THIS is how you wish people ill:
"May your teenage daughter start dating a drummer."
"Have another piece of pie--it might be the final straw that gives you diabetes!"
"May your job be outsourced and your house foreclosed on."
"I hope they declare caffeine an illegal drug, so you can never have coffee again."
Back in the trenches during First World War, some of the German and English troops declared a ceasefire on one Christmas Eve. It wasn't something that the officers ordered; they simply... didn't feel like fighting. They even played a game of soccer on the silent battlefield on Christmas Day.
If they could do that, why can't we declare a ceasefire in the culture wars for a couple of weeks?
Oh, and if you think of another really good ill-wishing, please post that in the comments, too.