At my current job, they were planning on going to a bar for our Christmas party. It took a lot of guts, but I actually emailed my boss saying "feel free if that's what you want to do." And he understood and they ended up changing their plans. Don't apologize for who you are and what your beliefs are. Frame them in a way that's very personal so someone who's in front of you doesn't feel like you're looking down on them.
Basically, Ireland has discarded its nice little religious holiday and imported some North American version, from the green beer and leprechauns to the Chinese-made plastic green shite and pools of vomit everywhere. This revelation shocked me