The thing is, when adherence to a community is enforced (even if just through social pressure), you'll get a lot of uncommitted people who might even wish they would share the values, but don't.
Atheists as a whole might be less likely to share a system of values, but those who sought and joined such an organization of their own volition (and not because their family dragged them to church every Sunday) are extremely likely to shared its values.
Atheists as a whole might be less likely to share a system of values, but those who sought and joined such an organization of their own volition (and not because their family dragged them to church every Sunday) are extremely likely to shared its values.