One of my favorite concepts I read about in the Book of Mormon is the prayers of the righteous affecting the unrighteous. We've read before that Alma the younger was visited by an angel because his father prayed that would happen, and the his son would have a change of heart. In this chapter, we are reading about the missionary companionship of Alma and Amulek and their preaching to the people of Amonihah. From the reprimanding that is taking place, we can infer that these people weren't too righteous, and they needed to be told to change. In fact, they are told they are so wicked that it is only because of the righteous prayers of those who are keeping the commandments that is keeping them all from being wiped out by a flood, or famine, pestilences.
Amulek tells them if they try to kick the righteous out of the city, or if they kill them, not only are they condemning themselves further by sinning more, but also removing their righteous prayer protection.
From this we can learn two things that are applicable today. First, if we have a friend or family member who is not making good decisions, we can be assured that our prayers are affecting them, even if they aren't returning to righteousness, they are protected by our love and prayers.
Secondly, if we ourselves are choosing unrighteousness (let's hope we aren't), we need to be considerate of those who are righteous and keep them safe from harm. They may be the only thing holding back God's wrath from us!