Wow. If you get annoyed over that, you wouldn't last long in a place like this. At any given time there is some kind of Muslim, Hindu, Buddhist, or Christian holiday going on. We get cards, gifts, etc. from people who celebrate all of them.
We are also invited to their holiday parties. I've been to Deepavali celebrations and Hari Raya and oodles of Chinese New Year parties. I consider it an honor to be invited or receive a card or a gift from these people even though we are of different faiths.
I am trying to picture myself opening a card from one of my Hindu students that says "Happy Deepavali" and thinking, "Ugh, how annoying!! They KNOW I am Christian!" and then tossing it in the trash.
Nope. Can't picture it.
I should probably go into work tomorrow and tell my boss that we wasted our time signing by hand (no fancy signature stamp) over 1000 Christmas cards that go out to everyone from parents to vendors we work with to local businesses (most of whom are not Christian). Don't want to annoy them.