Ask a lifelong (irreligious) atheist

[robvalue]

It's a bit hard to imagine since I don't have any and won't, but I'll answer hypothetically as best I can.

I'd respect their decision. I'd be there if they wanted to talk about it. Especially if they were young, I'd be on the lookout for any harm or duress being done to them, or that they may be causing. I'd address any such issues appropriately. If I felt there were none, then that would be fine.

I'd probably wonder what exactly had happened, and how the critical thinking I'd encouraged had failed, but that would ultimately be my issue not theirs.