And yet, puritanical Catholicism that fixates on policing sexual morality and claims to be the victim of a godless secular culture is unlikely to help the church flourish. Nearly 10 percent of U.S. adults are former Catholics, which makes them the third-largest U.S. “denomination.”

Even some bishops are sounding the alarm. Cardinal Carlo Martini of Milan, in a final interview before his death this summer, lamented that the church is “200 years out of date” and so focused on lecturing about sexuality that its leaders are in danger of being perceived as a “caricature in the media.”

U.S. Catholics bishops make wonderful statements about the importance of unions, comprehensive immigration reform and the need to protect social safety nets now threatened by anti-government ideologues. In letters to Congress, they have described a budget proposal by Rep. Paul Ryan, R-Wis., a Catholic now vying for the vice presidency, as failing “a basic moral test.”

But compared to the church’s frequent public denunciations of “pro-choice” Democrats or its two-week Fortnight for Freedom campaign — launched with special masses across the country in response to the Obama administration’s contraception coverage requirements under healthcare reform — the bishops have put little institutional muscle behind challenging a GOP economic agenda that is anathema to Catholic social teaching.

Even the U.S. bishops’ respected anti-poverty agency has been pressured by conservative Catholic activists to put ideology before care for the poor. A small nonprofit group in rural Colorado that helps Latino immigrants with healthcare and other basic needs lost more than half its funding from the Catholic Church because the group has an association with a statewide coalition that also happens to support gay rights.

Meanwhile, in a flashback to the McCarthy era, the Diocese of Arlington, Va., has required Sunday school teachers to swear loyalty oaths.

In the face of this embattled, defensive Catholicism, it’s no wonder that many Catholics have been cheering as a Nuns on the Bus tour rolled through several states this summer and into the fall. The trip highlighted the inspiring work sisters do in leading service agencies that feed the hungry and care for the sick.

“Preach the Gospel always and when necessary use words,” St. Francis of Assisi instructed. These nuns live that admonition every day. By challenging members of Congress who voted for Ryan’s draconian budget (which slashes nutrition programs for low-income women and infants), and by supporting the Affordable Care Act, the nuns also showed that being “pro-life” doesn’t stop with defending life in the womb.

Five decades removed from the aura of hope that animated Vatican II, the Catholic Church stands at a crossroads. Do the Vatican and U.S. bishops really want a smaller, “purer” church, where the door is slammed in the faces of nuns, theologians and progressive Catholics? Catholicism has few better ambassadors than the nuns on the bus. Our church marginalizes them at its own peril.

John Gehring is Catholic program director at Faith in Public Life, an advocacy group in Washington, and a former assistant director for media relations at the U.S. Conference of Catholic Bishops.