Tom Joad - The Truth
A Brief Background
This may come as a surprise to some readers, given that for a good portion of his life, Tom was away in prison, separated from society; this, however, is the most interesting factor about Tom: despite him being in prison for a long portion of his and his family's life, he still maintains a reputable basis of knowledge of the world he came into. Some would even argue that Tom manages to be more aware of his surroundings than other members of the Joad family, which is why he is viewed as a moral character of the story.
In the novel the narrator explains : "Al knew that even he had inspired some admiration among boys of his own age because his brother had killed a man" (84 Steinbeck). While Al's motives for looking up to his brother may be questionable, he -without a doubt- still views Tom as a morally acceptable and "good" person. The idea of Tom killing a man adds more of a "badass" vibe to his older brother, which makes Tom more admirable to Al.
While it could be argued that Tom is not a moral man given his prison sentence, his killing was in self defense. Tom doesn't allow all the rumors to get to him, as he claims in the aforementioned quote that he stands by his choices. Tom believes that people - or at least he - should be honest and stand behind their decisions. He remarks how he would kill Herb again in self defense because it was morally justified - after all, Herb attacked him first. In hindsight, Tom can be viewed as a moral, honest member of the Joad family.
Steinbeck, John. The Grapes of Wrath. New York, New York: Penguin Group, 1992.