I hope that the cynicism I reject in my own self-examination of my membership in my own church of rational physics engineering leads me to reject cynicism when trying to understand other people's churches. There ARE reasons people believe things and they are by no means all stupid reasons.

We're definitely in agreement there. And even the ones that are stupid may be psychologically reassuring or otherwise "make sense" even if they are completely irrational. While signalling arguments are important, I think it's unrealistic to consider them to the exclusion of other arguments.