God has affixed deadly consequences to the breaking of any of his commands regardless of how minor we might view them.
Cursed is every one that continueth not in all things which are written in the book of the law to do them
Note how all-inclusive it is. It applies to everyone who does not continue to do all of the commandments. It also shows that trying is not good enough. People not only have to do them, or do them once in a while; they have to continue to do them. Loving one enemy once doesn’t cut it. A person must love every person all the time. Otherwise, they are under God’s curse.
Since Mormonism teaches that nearly everybody goes to one of the three kingdoms of heaven, most Mormons have never entertained the thought they might not go to heaven. Therefore, you need to show them the dire straits Mormonism has put them in, namely, that they are on the road to hell.
Mormons don’t talk much about hell and when they do, many times, they use it to describe the temporary suffering people experience in spirit prison in the spirit world. (If you haven’t done so, it might be good for you to watch the video lessons on Mormonism’s plan of salvation.)
The closest thing in Mormonism to the biblical concept of a permanent hell is outer darkness. In Mormonism, however, outer darkness is reserved for only those who leave Mormonism and speak against it. Therefore, most Mormons never give a second thought of going there. Your task is to tell them this is exactly where Mormonism is leading them.
That they are on the road to outer darkness is one of the hardest but also one of the most important topics you need to discuss with them. Most Mormons won’t view anything you say as seriously as you take it until they understand the eternal stakes involved. This is only natural. People first have to know they are in trouble before they become serious about finding help. Out of love, we have to show them the deep trouble they are in.
Because this is such a difficult topic, pray that the Lord gives you the right opportunity to broach the subject. Talking about it too early, before the relationship has been established, could easily destroy the relationship. Because of the difficulty of the topic, most people are not inclined to bring it up too early. More commonly, people hesitate to ever bring it up. Waiting too long, however, will naturally lessen the impact of anything you say because the missionaries won’t see the danger they are in. This will then increase your frustration because they won’t take the discussions as seriously as you take them.
As you talk about outer darkness, do it with a tear in your eye. Go out of your way to show them you are speaking out of love and not anger. We refer to this as the love of warning. Think of a doctor who tells his patient that she has cancer. The loving thing for the doctor to do is to clearly tell her about her cancer. It would be the height of callousness for the doctor to tell her nothing was wrong because he didn’t want to cause her distress. This is especially true when a cure is readily available! Such a doctor would be sued for malpractice, if not imprisoned.