First there is Steinbeck's original purpose in "In dubious Battle". Steinbeck like Hemingway, Dos Passos and a lot of other lefties and semi-lefties was, indeed quite sympathetic to workers and the dispossessed but THEY WERE ABSOLUTELY DISGUSTED WITH THE COMMUNISTS AND, FOR THE MOST PART THE IWW. They came by this disdain observing American labor struggles and especially in the Spanish Civil War. What they hated is almost turned backwards in this movie. For Steinbeck and the others the reds were agents provocateurs provoking violence against labor and liberals in the hope of provoking revolution. They were cowards, too baiting liberal (i.e. republican and democratic) forces into traps, into slaughter while pretending to be their allies. The reds provked battles then and let their official enemies and their supposed friends to slaughter one another leaving a clearer opportunity for the reds to try to seize power. For all Steinbeck's sympathies (which I tend to share) he was a genuine liberal and detested collectivism and Communists. That is why he titled the short work "In DUBIOUS Battle" Dubious as in fake, not what it seemed to be, not really for it's supposed beneficiaries.
Beyond that are ridiculous errors in staging and continuity. It is supposed to be apple harvest in the northwest. That is in the fall. Yet the fields are tall with fresh young grass (Timothy I believe). Deciduous trees are leafing out with fresh, young green leaves, there are no deciduous trees losing leaves or showing fall colors; in fact several scenes show flower buds on tree branches. It is obviously spring. Did they glue the apples on the trees? As to continuity, someone walks into a tent dressed one way then exits, his or her garb is suddenly, conspicuously different. This also happens with background and some crowd scenes. This is a simple matter of craftsmanship which should be much better in a production that seemed to have a reasonably generous budget. Continuity this bad is so jarring that it distracts from the movie. I'll add that the performances are not really good except for Sam Shepard's and Robert Duvall's. Selena Gomez is a beautiful girl - too beautiful for this role and too girl - she looks like a very pretty, sexy twelve year old and I felt kind of icky seeing her cast in this role.