We Americans think of ourselves as living in a moment of deep polarization around issues of religion and politics, and we do. But the roots of the crisis go back decades. For decades, conservatives, including religious conservatives, have complained that the mainstream media, which has a huge influence in our culture, is biased against them, and so cannot be trusted. It’s not simply a matter of how the media reports stories; it’s how the media chooses which stories and people to cover, and which not to cover. Professional journalists have rejected the criticism and insisted that they have acted, to the extent possible, in a neutral way. Conservatives have never been convinced, which is why today’s progressive complaints about media bias seem to them a little hollow, and tardy.

This month, Harvard releases a history of media in the 1960s and 70s that seems, more or less, to support the conservative criticism: On Press: The Liberal Values That Shaped the News, by Seton Hall journalism professor Matthew Pressman. Pressman argues that the media very self-consciously adopted liberal positions during those years, with the best of motives. “Objectivity and impartiality, the cornerstones of journalistic principle, were not jettisoned,” the description reassures us, only “reimagined.” Which is just what conservatives always maintained–though they didn’t find the reimagination reassuring. Here’s the description of the book from the Harvard website:

In the 1960s and 1970s, the American press embraced a new way of reporting and selling the news. The causes were many: the proliferation of television, pressure to rectify the news media’s dismal treatment of minorities and women, accusations of bias from left and right, and the migration of affluent subscribers to suburbs. As Matthew Pressman’s timely history reveals, during these tumultuous decades the core values that held the profession together broke apart, and the distinctive characteristics of contemporary American journalism emerged.

Simply reporting the facts was no longer enough. In a country facing assassinations, a failing war in Vietnam, and presidential impeachment, reporters recognized a pressing need to interpret and analyze events for their readers. Objectivity and impartiality, the cornerstones of journalistic principle, were not jettisoned, but they were reimagined. Journalists’ adoption of an adversarial relationship with government and big business, along with sympathy for the dispossessed, gave their reporting a distinctly liberal drift. Yet at the same time, “soft news”—lifestyle, arts, entertainment—moved to the forefront of editors’ concerns, as profits took precedence over politics.

Today, the American press stands once again at a precipice. Accusations of political bias are more rampant than ever, and there are increasing calls from activists, customers, advertisers, and reporters themselves to rethink the values that drive the industry. As On Press suggests, today’s controversies—the latest iteration of debates that began a half-century ago—will likely take the press in unforeseen directions and challenge its survival.