The article is here; the Abstract:
Speech damages someone's reputation when it leads others to believe that that person has done something that reflects poorly on their character. When that belief is also false the reputational damage is undeserved, and it is the point of American defamation law to protect individuals from suffering such undeserved reputational damage.
It is easy to understand why individuals would need protection from false and derogatory claims made about them in works of nonfiction, such as journalism, documentaries, and biographies. But it is not immediately clear why individuals would also need protection from fiction. Although authors of fiction often base their fictional characters on real people, they do not typically make real people characters in their stories. Even when they do put real people in their stories and depict them as doing bad things, the audience is still usually meant only to imagine the real people doing those bad things.
Nevertheless, some works of fiction are not only about real people but also do real and undeserved damage to their reputations. It may not be true, as has often been alleged, that Aristophanes's comedy The Clouds gave Socrates the reputation for rejecting the gods and corrupting the young that later led to his execution. But readers of parodies of news articles published on sites like The Onion and The Babylon Bee are sometimes duped, especially when they are already inclined to think poorly of the public figure that is being ridiculed.
Of course parodies are believed only when they are not recognized as parodies. But there are other genres of fiction that mix facts into the story, such as biofiction, biopics, and docudramas, and it is not always easy for audiences to distinguish what the author is making up from what the author is, or ought to be, trying to get right.