The Book of Mormon establishes social equality as an ideal. This is not social equalness. There is no suggestion that all people are the same, only that we should not act as though we are superior to others. The damage is not in the difference, but in the attitude of separation. Therefore, Benjamin notes that if one does not share his or her substance because of selfishness, their “substance shall perish with [them].” Of course, that is true of all, but the point is that when one thinks of oneself as valuable because of their possessions, when they leave those possessions behind in death, there is nothing left of value because of the poverty of character.
This is emphasized by noting that it is even possible for those without means to be selfish. The solution is that when one is asked for help, the desire to help even in the absence of ability is superior. That development of character cannot be removed through death.