I agree completely with the response above. I don't think there is anyway we can see Steinbeck as a neutral observer. He very clearly and very purposefully set out to be just the opposite in The Grapes of Wrath. His research into the plight of the "Okies" and his own journey along Route 66 to provide authenticity to the novel's descriptions and plot line was extensive. He clearly wants the reader to feel empathy and compassion for the Joads and the others like them for not only their condition in life and also wants them to feel anger at the banks, the large farms, the capitalists. etc. who have created these conditions as well.
In fact, much of the criticism of The Grapes of Wrath stems from the fact that the novel is such a one-sided portrayal. Some have gone so far as to label the novel as propaganda because of this fact.
Steinbeck, in The Grapes of Wrath, is not in any way a neutral observer. Or, at least, his narrator is not a neutral observer.
The novel presents what it presents from only one side. It is not a fair representation of both sides of the story. The work spends no time presenting the point of view of the owners of the lands, etc., featured in the book. Everything is from the Joads' point of view. The Joads are the heroes and the owners are the villains.
Some writers and scholars believe that the one thing a novel can do that no other art form can do is present a fair and thorough presentation of all sides in a conflict. This kind of novel most fully reveals the human condition, or human existence. Whether you agree with that or not, it is certain that Steinbeck's novel is not that kind.
His novel is designed to present the plight of the victims of the dust bowl, the depression, etc. It is not at all written to reveal anything from the point of view of the landowners and business owners.