He didn't want to arrest his own brother that everyone loved, not only would his parents be mad at him but it would make him look like the bad guy and he knew that. Wes decided to do the “right thing” by arresting him but only putting him in the basement. He tried to stay loyal to his brother and show him at least some respect by not placing him in real jail, which he didn’t deserve. Wes stopped him from doing any more Indian girls wrong, and he was proud of himself for doing that much, but he still felt bad because it was his brother, and his parents, dad specifically, hated that he would do that to his own brother. Through this whole ordeal, David knew what was going on, and he knew his dad was doing what he thought was right, but David himself was disgusted, he didn't think his uncle Frank would do a thing like that.
I think what Wes did wasn't exactly right, but I think he would have made a difference. He wanted to protect his family, which he looked at Marie as if she was part of the family, but he still wanted to serve his country. He made the decision that he had to take action and stop his brother from abusing his power and taking advantage of those Indian girls. The theme says a lot about this story and it shows that sometimes you have to make a harsh decision even if it goes against your loyalty towards family, friends,