If you are an atheist this isn't going against any of your "religious" beliefs, so how could this offend you? Even if it did, understand you are in the minority, grow some skin and deal with it.
I've been in crowds where I am the odd man out; recently was at a festive in Chicago where a jewish prayer was said. Did I get all flustered? No, I stood there and ACCEPTED that people have different beliefs. Accept it and move on(without crying about it).
So being in a minority means I’m supposed to be quiet? Is that also your attitude toward political positions that don’t conform to the majority? Do you realize where you are??
Re your example: What is a “festive”?