Liberalism and Mainline decline
In response to the story that "liberalism" of the 60s has caused mainline decline: But the move to a liberal understanding of faith probably dates back to the late 1700s, the late 1800s in a more recognizable form.
Walking through a divinity school in 1907 you would likely hear far more doubt about basic Christian doctrines and their traditional articulation than you would hear in 2007.
Before there was the National Council of Churches, there was the Federal Council of Churches. The sort of social witness groups, such as Methodist Federation for Social Action, were created around the turn of the last century.
This is all to say that I've noticed the propensity of baby boomers both left and right seem to think that anything of importance must have happened since the 1960s. And since the 60s coincides with the fall off of mainline membership it works great for a certain narrative.
But there was religious liberalism before the membership decline. And there are conservative mainline churches like the Missouri Synod Lutherans who face the same drop off situation and in some respects the Southern Baptists as well.
And of course there are liberal religious groups growing such as Reform Judaism. More interesting is the fact that folks not identifying with any religion has doubled over the last decade or so. That's the biggest growth your seeing.
Having one group of Christians relishing over their growth numbers (which has little or no relation to any Gospel rational) and rejoicing against mainline numbers shows alack of charity and avoids the issue of the overall decline of religious identification in this country.