The point of The Jungle is to persuade you to think a certain way about a set of social issues. Therefore, it makes sense that the author is not shy about just coming out and telling you straight out what he thinks of the characters and their situations. So, Ona is "one of god's gentlest creatures" (1.2); Teta Elzbieta is "a wonderfully wise little woman" (30.1); Antanas Rudkus is "the meekest man that God ever put on earth" (5.16), and so on. These are outright descriptions of character traits; the narrator just straight up tells us what these people are like.
In the world of The Jungle, the workingman has total moral authority. Even workingmen who do bad things – like Jurgis with his election rigging or Marija and her prostitution – are given economic and social explanations for how they have gone bad. When they do wrong, their poor moral character and even their behavior towards other people is largely the result of their impoverished and oppressed social status. The dominant characteristic that distinguishes these figures is their position at the bottom of the social hierarchy, which makes them objects of pity and empathy for socialist Upton Sinclair.
By contrast, foremen and factory managers are much less sympathetic characters. Since they willingly victimize the lower orders, everyone in the upper classes appears to be abusive and cruel (see Connor and Miss Henderson for examples). The only exceptions to this rule are men who deliberately flout their social status to assist the socialist cause – men like Fisher the millionaire (who has given away all of his money to charity) and Tommy Hinds the socialist hotel owner.
Criminals are outside of established social hierarchies, so they are harder to judge: Jack Duane is one of the only characters who expresses unselfish brotherhood with Jurgis, but he is also totally willing to leave his mugging victims lying unconscious in the streets of Chicago.
Poet John Donne tells us no man is an island. Novelist Upton Sinclair would reply: no, but in a capitalist system, he should be for his own sake. In other words, a lot of the criticism of bad business practice in this novel dwells on how business wrecks families. The efforts of good people to support their families says a lot about what kind of people they are, but it also indicates that they are in for some suffering. Think of poor Marija Berczynskas. If she had ditched Ona and Teta Elzbieta and the rest when she was making some money and engaged to Tamoszius Kuszleika, she might have been able to marry him and have a good life. Yet, because she tried to help her family, their marriage got put off indefinitely and disaster eventually struck.
By contrast, the bad people of the novel are generally selfish and have no family ties: think of Jones and his tyrannical behavior to his children, or even criminal Jack Duane, who has abandoned his mother and sister. When Jurgis is at his lowest point morally (with the mugging the election rigging) he has also lost all touch with Marija, Teta Elzbieta, and the rest. Once he's hit bottom and on the way to socialism, he reestablishes connections with those characters. Socialism is all about group health over the individual's profit, while capitalism is about individual success rather than group benefit. The family is a very small group. So it is in line with Upton Sinclair's political agenda that capitalism (which is individualistic) destroys families, while socialism (which is group-oriented) is focused on the brotherhood of all mankind.