Here (via Michelle Malkin) is a great idea from Kevin:
We are excited to be launching the opportunity today...between now and Christmas we are asking you to send the ACLU direct "MerryChristmas" cards.Head on over to Kevin's blog to get the address for the card writing campaign.
And we aren't talking about these generic "happy holiday" (meaning nothing) type of cards...
Go get as "Christmas" a Christmas card as you can find... something that says.. "Joy To The World", "For Unto Us A Child Is Born", but at least "Merry Christmas", put some of your own thoughts into it, sign it respectfully and zip it off in the mail...
And be nice! As it is written in the Bible, it will be like heaping ashes on their heads... far more than any snotty comment one could conceive.
UPDATE: Perhaps they will reciprocate with a "Blandly Inoffensive, Politically Correct, Generic Seasonal Greeting" card of their own. Or not. I won't hold my breath.
(Adapted from a comment I left at Myopic Zeal)