People who disagree with same-sex marriage and birth-control use have been met with accusations of bigotry. Are some Christians being unfairly shamed out of the public sphere? Is evangelical Christian morality still viable in American public life? This is the question lurking in recent debates over religious-liberty issues, from the Supreme Court’s Hobby Lobby decision to the Christian bakers who object to baking cakes for gay weddings. In discussions of these cases, objections to same-sex marriage and contraception are described as a retreat from “secular society.” And in some cases, evangelicals actually have retreated: Since the Boy Scouts of America...