Joseph Fielding Smith, Gospel Doctrine, Pg.310-311) "There are said to be more shades of green than of any other color, so also we are of the opinion there are more grades or degrees of sin associated with the improper relationship of the sexes than of any other wrongdoing of which we have knowledge. They all involve a grave offense -- the sin against chastity, but in numerous instances this sin is intensified by the breaking of sacred covenants, to which is sometimes added deceit, intimidation or actual violence.
Much as all these sins are to be denounced and deplored, we can ourselves see a difference both in intent and consequence between the offense of a young couple who, being betrothed, in an unguarded moment, without premeditation fall into sin, and that of the man who having entered into holy places and made sacred covenants, plots to rob the wife of his neighbor of her virtue either by cunning or force and accomplish his vile intent.
Not only is there a difference in these wrongs, judging from the standpoint of intent, but also from that of the consequences. In the first instance the young couple who have transgressed can make partial amends by sincere repentance and by marrying. One reparation, however, they cannot make. They cannot restore the respect that they previously held for each other; and too often as a consequence of this loss of confidence their married life is clouded or embittered by the fear that each has for the other, having once sinned, may do so again. In the other case, others are most disastrously involved, families are broken up, misery is forced upon innocent parties, society is affected, doubt is thrown upon the paternity of children, and from the standpoint of gospel ordinances, the question of descent is clouded and pedigrees become worthless; altogether, wrongs are committed both to the living and the dead, as well as to the yet unborn, which it is out of the power of the offenders to repair or make right.
Sometimes an argument is advanced to limit the provisions of the law of God, as given in the book of Doctrine and Covenants, both with regard to punishment and to forgiveness to those who have entered the House of the Lord and received their endowments. This is not possible, as so many of these provisions were given in revelations published several years before the Saints were permitted to receive these holy ordinances, indeed, before any temple was built. The law as given, we believe to be general, applying to all the Saints. But undoubtedly when, in addition to the actual offense against the laws of chastity, covenants are broken, then the punishment for the double offense will, either in this life or that which is to come, be correspondingly greater and more severe." -- Juvenile Instructor, Nov. 15, 1902, Vol. 37, p. 688.
Some may argue with the topic in general. For example, I think these days pushing marriage on a couple as a condition of repentance may not be prudent. But at least he acknowledges that younger people who may cave in are not hideous and he does not put them next to murder. The idea of varying degrees on this sin ought to be more of a theme when teaching the youth