You're very unhappy with the idea that Christmas exists. The vast majority of the rest of the world, including the vast majority of us, is unhappy with the idea that it appears George W Bush has been elected. (Unless we can prove massive fraud).
We both have to live with these facts.
It seems to me you only have grounds for complaint if, after your cheery response of "Bugger off", somebody for the second time tells you "Merry Christmas".
Unless of course you're another one with a lot of pent-up rage. (We already have one.) And I suspect, not just at Christmas.
But thanks for being willing to differentiate yourself from the amorphous mass of nameless Guests we're honored to have.