The film Oh Brother Where Art Thou? presents various aspects of southern, depression era life in a farcical way.
Southern politicians are portrayed as conniving, scheming crooks. In contrast, the criminals stand out as being simple, good hearted, and virtuous.
The women in the film are either impossible to please with a practicality bordering on frigidity, or ensnaring dangerous creatures that will charm men right out of their cloths and into making bad decisions and abandoning their friends.
Country music is shown as an art form that takes no thought at all. In fact the main characters seem to pull the hit song "Man of Constant Sorrow" directly out of their ‘you know what.’ Music is also shown in the film as a political tool that can rally the people to a political cause without involving actual politics.
Both the law and the KKK are portrayed to be evil and devilish. The KKK members are crushed by their own burning cross in one scene. A comparison is made between Sheriff Cooley and the devil himself, who encounters Tommy Johnson and takes his soul in return for the skill to play a guitar. The eNotes/Wikipedia page on the film says the following:
Tommy describes the devil as being "White, as white as you folks ... with empty eyes and a big hollow voice. He love to travel around with a mean old hound". This description just so happens to match Sheriff Cooley, the policeman who is pursuing the trio.
Blacks are portrayed as good people who are constantly pursued unjustly by the whites for no reason.
Family life is important in the context of the movie. The characters take their responsibilities to their families seriously, but they often seem oblivious to what is really best for them.