Two years ago, renowned historian David J. Garrow was dismissive of newly released FBI files claiming Martin Luther King Jr. was a “whole-hearted” communist.

“The number one thing I’ve learned in 40 years of doing this,” Garrow said in an interview with The Washington Post, “is just because you see it in a top-secret document, just because someone had said it to the FBI, doesn’t mean it’s all accurate.”

Garrow, 66, who won a Pulitzer Prize for “Bearing the Cross,” his 1986 biography of King, noted that FBI Director J. Edgar Hoover was out to discredit the civil rights leader and said FBI files should be treated with skepticism.

As he faces a wave of criticism from other historians for an essay published Thursday in Standpoint, a conservative British cultural magazine, he now says some FBI files are more reliable than others.

Garrow claims new evidence shows King, whose extramarital affairs have long been known, was a “sexual libertine,” alleging sexual activities with dozens of women and describing them in graphic detail. One of the claims would constitute a crime if true.

His evidence? FBI files purported to be summaries of recordings of King and his colleagues in the 1960s when their rooms were being bugged and phones wiretapped by Hoover. The summaries were apparently inadvertently included in the John F. Kennedy files maintained by the National Archives and released online in 2017 and 2018. Garrow discovered the inadvertent release.