At the end of Roll of Thunder, Hear My Cry, Papa is in an almost impossible situation. T.J. is about to be lynched by a group of white men, and Stacey is in danger as well. By setting his own cotton on fire, Papa avoids a fight that would almost certainly end in his own death. The fire distracts the lynch mob because the members of the mob, all farmers, are afraid the fire will spread out of Papa’s land and into the nearby cotton fields.
Setting a fire on purpose is arson; it’s illegal. It is usually wrong to do things that are against the law, but Papa lives in an unfair world. The law does not protect him, his family, or his neighbors just because they are black. Papa’s decision to set the fire saves T.J. from the lynch mob and brings less danger to the Logan family than a fight would.
I believe that Papa’s choice to break the law is justified because there is no legal way for him to protect himself.