But for those who could suffer backlash as a non-believer, you could answer in a way that is technically correct, something like, "I don't think I attend the church you do," smile, and change the subject to something less controversial, like politics.
What science can tell us is that all the observable universe dates back to around 13.8 billion years ago, and commenced in a burp when the matter/energy/spacetime we can see originated. But from what?
Civility is at heart being honest and kind. Civility is not failing to call out ignorance, or hiding one's deep convictions, but how those are presented in public.
Why do most atheists ask annoyingly hard questions like, 'if God created man then who created God?,' the moment someone reveals that they're Christian?