Posthumous cults can be dangerously misleading. Such is the message, whether intentional or not, of “Prophet Singer: The Voice and Vision of Woody Guthrie” by Mark Allan Jackson (University Press of Mississippi, 303 pages, $50). This new study analyzes the legacy of Guthrie (1912–1967), who wrote the famous populist empowerment anthem, “This Land Is Your Land.” Guthrie, a scrawny, frizzy-haired folkie from Oklahoma whose lack of personal hygiene was a joke among musical colleagues, sang with an authentic twang against power-grubbers. For a time, his guitar was decorated with a sign: “This Machine Kills Fascists.” This musical bravado was in distinct contrast with Guthrie’s own puny — although heartfelt — stage presence. In his posthumously-compiled 1976 book, “Born to Win,” Guthrie calls himself a “prophetsinger” with a certain amount of irony. Likewise, in the song “Pass Away,” Guthrie claims with wry braggadocio that “no word of mine shall ever pass away.” Today’s worshipful fans show signs of taking him literally, without a trace of his appealing self-mockery.

In 2005, a lavish coffee table book was published, “Woody Guthrie Artworks,” containing painstakingly reproduced sketches for newspaper cartoons, which might best be described as glorified doodles. The year before, Penguin reissued “Bound for Glory,” Guthrie’s 1943 novel about his years spent hitchhiking and riding rails west to California during the “Dust Bowl” days of the Great Depression, alongside hobos, dispossessed farmers, and other victims of the capitalist system. Today in Manhattan, at the distinctly unpopulist address of 250 W. 57th St., where commercial rents have reached $5,300 per square foot, resides the Woody Guthrie Foundation and Archives.

Yet these celebrations pall somewhat when juxtaposed with “Prophet Singer: The Voice and Vision of Woody Guthrie.” Mark Allan Jackson, who teaches English at West Virginia University, informs us that in early radio appearances, Guthrie exhibited bigoted behavior, describing Mexicans as “pepper-bellies” and African-Americans as “darkies.” In a homemade newspaper from 1936, Guthrie describes an integrated beach with an “Ethiopian smell” emitted by African-Americans, whom he calls “monkeys” and “chocolate drops.” Even some Guthrie songs reflected this kind of racism, such as his 1937 song “The Chinese and the Japs,” which contains the couplet: “If they bombard good old Tokio — Well, I guess that’s okie dokio.”

Historians find it less okie dokio that Guthrie wrote ballads glorifying villains such as Billy the Kid and Pretty Boy Floyd as Robin Hood figures, whereas in fact such bad guys stole from everyone and kept everything. In “Hard Times in the Subway,” a 1943 tune glorifying a transit strike, New York mayor Fiorello LaGuardia is ridiculously described as a fascist, indeed Hitlerian, because he opposed pay hikes for workers. Of course, in 1943 Guthrie was a relative newcomer to New York and might have been ignorant of La-Guardia’s strenuous antifascism. He might also have believed yet another bigoted generalization of the time, that all Italian-Americans were fascists. Still another song, which Guthrie popularized and constantly performed, although he did not write it, “Hobo’s Lullaby,” contains the exclusionist, indeed inhuman lines: “But when you die and go to Heaven / You’ll find no policemen there.”

Other critics today feel uncomfortable about Guthrie’s unbridled sex life, exemplified by the posthumously published song “Ingrid Bergman,” inspired by that actress’s 1950 film “Stromboli,” which was set on an island with an active volcano. With comic lewdness, Guthrie addresses Bergman: “You’d make my fire fly from the crater. / This old mountain it’s been waiting … For your hand to touch the hardrock.” The American folklorist Ellen Steckert recently decried Guthrie’s “sexism, a recurrent motif in his writings and in his life.” Demanding posthumous orthodoxy — and political correctness — from Guthrie is clearly futile, however fashionable.

A more direct and enjoyable legacy from Guthrie is his son Arlo, who turns 60 later this year. Now white-haired, Arlo still sings with youthful humor his 1967 anti-Vietnam War blues song, “Alice’s Restaurant,” in concerts and on CDs. Leavened with good-natured joshing in a way that many of his father’s worshipers seem unable or unwilling to maintain, Arlo Guthrie’s performances are living proof that one need not be a selfserious “prophet” to spread the good word.

Mr. Ivry last wrote in these pages on the poet Zbigniew Herbert.