Thanks for the responses

"Woody is just Woody. Thousands of people do not know he has any other name. He is just a voice and a guitar. He sings the songs of a people and I suspect that he is, in a way, that people. Harsh voiced and nasal, his guitar hanging like a tire iron on a rusty rim, there is nothing sweet about Woody, and there is nothing sweet about the songs he sings. But there is something more important for those who will listen. There is the will of the people to endure and fight against oppression. I think we call this the American spirit."
John Steinbeck; quoted in Joe Klein, Woody Guthrie: A Life, London, 1981, p. 160.
and at http://www. geocities.com/Nashville/3448/guthrie.html
or alternatively http://www.fortunecity.com/tinpan/parton/2/guthrie.html

Guthrie had a similar regard for Steinbeck (or at least for the film based on a Steinbeck film). The fact that Guthrie was commissioned to write a song about the Grapes of Wrath should not make us think that Guthrie did not already hold the film in esteem. The Tom Joad page of the afore-mentioned Guthrie website* gives the story of the song's composition in both Guthrie's and Pete Seeger's words, but it also quotes a Guthrie People's World column circa 1940 which praises the film most highly. (*scroll down the page and click on Tom Joad)