Christianity is in decline in the United States. The share of Americans who describe themselves as Christians and attend church is dropping. Evangelical voters make up a smaller share of the electorate. Members of the millennial generation are detaching themselves from religious institutions in droves.

Christianity’s gravest setbacks are in the realm of values. American culture is shifting away from orthodox Christian positions on homosexuality, premarital sex, contraception, out-of-wedlock childbearing, divorce and a range of other social issues. More and more Christians feel estranged from mainstream culture. They fear they will soon be treated as social pariahs, the moral equivalent of segregationists because of their adherence to scriptural teaching on gay marriage. They fear their colleges will be decertified, their religious institutions will lose their tax-exempt status, their religious liberty will come under greater assault.

The Supreme Court’s gay marriage decision landed like some sort of culminating body blow onto this beleaguered climate. Rod Dreher, author of the truly outstanding book “How Dante Can Save Your Life,” wrote an essay in Time in which he argued that it was time for Christians to strategically retreat into their own communities, where they could keep “the light of faith burning through the surrounding cultural darkness.”

He continued: “We have to accept that we really are living in a culturally post-Christian nation. The fundamental norms Christians have long been able to depend on no longer exist.”