Why does Shane allow Chris to make fun of him when they meet at the bar?
Shane does not resort to violence or fighting unless every other option has been exhausted. It is not worth it to him to get further entangled in the mess with Fletcher, and he wants to avoid it if at all possible. He also knows that a fight will escalate the situation and perhaps endanger Joe. Shane's insight into this situation proves to be remarkable—when he finally does succumb to fighting with Chris he and Joe both get sucked into a potentially deadly situation.
Shane also realizes that Chris is just a boy. He even says that to Chris after he beats Chris up—that Chris has potential but is simply too young. Unlike Fletcher, who is a man but a bad man, Chris is only a bad boy and could still possibly grow up to be a man. It so happens that his experience with Shane serves as a catalyst for this very transformation.
Why is Joe not angry with Shane or Marian for having feelings for each other?
Joe has faith in both Shane and his wife. Despite their love for one another, they are both loyal and good people and neither would disrespect him so much as to be unfaithful. He knows that if anything does happen between the two, they would tell him first and be completely honest. At the end of the day he knows that Marian is also extremely devoted to Bob and would never break up the family. In addition to his trust in Shane and his wife, he also has to admit that objectively, Shane is a greater man. It is not a surprise that Marian should love him, and rather than being a shock, it is completely understandable to him.
In many ways, Marian's feelings for Shane are very similar to Joe's feelings for Shane. Both Joe and Marian love Shane as a person—they both respect him and they both appreciate what he brings to their family and their farm. Both acknowledge that he is a wonderful man and feel safe having him around. Similarly, Marian is a wonderful wife, and it does not surprise Joe that Shane appreciates that. Shane's past with women is a subject never mentioned in the book—no one knows if he has ever been married or been in love. Regardless, he enjoys Marian both for her role as wife and mother, but also as a person. Between the three of them there is a mutual appreciation for one another that all of them understand and to which none of them object.
What is Shane's role in Bob's development as a man?
Shane teaches Bob a number of things by example—to work hard, to be respectful, to finish what one has started, to be loyal, and that fighting is not the best way to solve problems. In addition to Shane's individual characteristics is the fact that Shane fills a particular space in Bob's life and in his formation. He is an example and a definition. Bob respects and admires his father, but having an unrelated, objective hero is another matter. Bob learns to distinguish between people like Fletcher and people like Shane, not only in terms of whom he admires but also in terms of who is more like the man he hopes to become someday. After he meets Shane, he has some basis to evaluate other people and to evaluate himself. Knowing Shane gives Bob a life- long goal and a personal agenda—he knows that he wants to be like Shane, both a man and a hero.