There are points on the political spectrum where the arcs of far right and far left converge: adherence to outlandish conspiracy theories, for one. Another troubling commonality is explored in an alarming new report from PEN America — a nonprofit whose 7,500 members include novelists, journalists, nonfiction writers, poets, editors, essayists, publishers and their associates.

The grave dangers recently posed to freedom of expression and the freedom to read by book-banning conservative zealots and state governments have been well-documented. Those core values of American democracy are anchored by First Amendment guarantees. But PEN America’s report, titled “Booklash: Literary Freedom, Online Outrage and the Language of Harm,” details another kind of threat arising from a different direction.

It reports that the terms of literary engagement have been transformed in recent years from the traditional type of critical reviews carried by newspapers and periodicals to the wild west of social media, where authors and their books can be blown up remorselessly by “reviewers” who take exception to the work, often without having bothered to read it. Online “review bombing” aimed at exploding an offending work even before publication is a hallmark of this new kind of literary warfare.

These public reviewers cite many objections to “problematic” content, but they generally boil down to two. One is whether particular authors have the “legitimacy” or “right” or “authority” to write about subjects and experiences associated with traditionally marginalized groups to which they do not belong. The second is the perceived harm that a given work might inflict on members of those groups.

Sometimes the vitriol is so toxic and so sustained that authors and/or their publishers end up withdrawing books or altering them to conform with current notions of what is permissible in literary discourse, thereby depriving other readers of the fundamental right to make their own judgments. Even classic works of literature are not immune. Some are being altered by publishers who do not want to risk offending modern sensibilities, thus undermining their historical value as reflections of their times. This is but another form of censorship, although not of the constitutionally prohibited governmental variety.

Concerns about the perpetuation of stereotypes in literature and questions about the authenticity of the experience depicted by authors are not without merit. But circumscribing the universe of people who can write about any particular subject is, as the report notes, “incompatible with the freedom to imagine that is essential to the creation of literature, and it denies readers the opportunity to experience stories through the eyes of writers offering varied and distinctive lenses.”

The notion that books can cause actual harm is where the censorious right and left meet, although from very different directions. Conservative book-banners believe that exposure to certain kinds of content — often that dealing with sexuality, race or gender — can be dangerous. In fact, a number of states have codified “harmful materials standards” in the course of banning certain works. But those committed to a progressive agenda of equity and inclusiveness also sometimes invoke the language of harm to describe literary conventions or tropes that they perceive as insensitive.

What these viewpoints have in common, PEN points out, is that they conflate harm with offense. When a threatened harm is generalized, when who is harmed and how is not specified, when the assertion is unencumbered by evidence — most likely the material is not harmful but rather has given offense. As the novelist Salman Rushdie, who has more than paid the price for giving offense during his notable career, puts it, “What is freedom of expression? Without the freedom to offend, it ceases to exist.”

Readers should rise to the defense of works that offend values, preconceptions and world views, even if — or maybe especially if — those values, preconceptions and world views are their own. Works that shake our intellectual, emotional and moral complacency are very often more valuable than those that reinforce pre-existing views.

Sad to say, some members of a rising progressive generation exhibit less commitment to freedom of expression than their predecessors, perhaps because they see free speech all too often used as a powerful tool of oppression wielded against the powerless. There is a grain of truth in this. But democracy rests on the bedrock faith that the average person, in literature as in life and politics, can distinguish between the bad and the good, and ultimately will choose correctly. That doesn’t always happen, but the best remedy for a bad book remains reading or writing a better one.