^^ Yeah, I might be more inclined to join in if it was the company paying the bill. However we have to pay for our own xmas lunch, and I'm not dead keen on paying £28 for food I don't even like, to sit with people I'm not super keen on. My best friend in the office won't be there so I have zero incentive to go.
Major religious groups
Pick one you like, and say it's against your beliefs while you look them dead in the eye. Always works for me.