According to the Pew Research Center, one-third of Americans under 30 have no religious affiliation. As Harvard professor Robert Putnam told Greene in the piece that kicked off the series, this trend among young people is tied to religion's association with socially conservative politics.

"I think the single most important reason for the rise of the unknowns is that combination of the younger people moving to the left on social issues and the most visible religious leaders moving to the right on that same issue."

Take Melissa Adelman, 30, a participant in a roundtable about religion that Greene had with six young adults. Adelman was raised Catholic but does not call herself one today because she cannot embrace the church's core beliefs on social issues.

"To me a church that would be welcoming would be one where there wasn't a male-only hierarchy that made all the rules, and there weren't these rules about who's excluded and who's included and what behavior is acceptable and what's not acceptable," she tells Greene.

In Friday's story, the Rev. Mike Baughman, a United Methodist minister who runs a Christian coffee shop in Dallas, tells Greene that the church is indeed sending the wrong message.

"If the church was known more for our efforts to welcome the stranger than keep them out, I think the church would have greater credibility with rising generations," says Baughman. "For example, on immigration policies, we've taken the wrong stance on that, and they know. The thing is they're smart enough. A lot of them have grown up in the church and then rejected it. They've read the scriptures that talk about the importance of welcoming the stranger, they've read the scriptures about the importance of caring for the poor, and when they see that no longer on the lips of those who are in religious authority, they see that the God we present is bankrupt, and that we're theologically thin in our ability to even speak our own story."