The problem with apostasy is that it forfeits truths which are necessary in order to comprehend the majesty of Christ's teachings. Those truths which get retained are not kept in balance with the rest. Simple virtues are kept while overall righteousness is forfeited.
No one can argue with the virtue of tolerance. But it is constrained and governed inside a larger context that prevents permissiveness and sloth.
No one can argue with the virtue of obedience. Indeed, obedience is itself one of the bedrock requirements of the Gospel. But divorced from the other virtues inside of which it is regulated, obedience can become a terrible weapon used to separate people from God's Holy Spirit and drive them into submission to "Popes and Priests." (Any man believed to be incapable of leading you into error is a "Pope.")
No one can argue against the virtue of patience. But when it is urged to prevent necessary action to develop a god-like people, then it has become a tool for deception and error and not a virtue at all.
Take any virtue and remove it from its overall context within the great Gospel whole and you see how apostasy can warp a people. They retain the conviction that they are still God's chosen disciples, because the virtues they practice are in fact, godly. However, they have become distorted, bloated and swollen. They are without harmony, capable of great evil or neglect, all the while celebrating their fidelity to the "truth" as they understand it.
You MUST understand doctrine. You MUST study the scriptures. But more important than anything else, you MUST seek to gain further light and knowledge by conversing with the Lord directly. Harmony of the whole is dependent upon His direct guidance and blessings. You simply cannot move forward a piece here and a bit there, while neglecting the whole composite picture of the Gospel. He will open it to your view. He will show you how one part is related to another, and that to another still, so that it all moves forward together. It is not to all be comprehended at once. It is to be gained a little bit of the whole here, a further harmony of things there, until the whole moves forward together. Always moving in balance, in harmony and as a complete magisterial revelation of God's will.
Latter-day Saints are not immune from this problem of disharmony. Indeed, it is the great challenge which we have faced since the time of the First Vision. Joseph's recalibrating of his own life was constant. He wanted to reward Martin Harris for his support, petitioned for permission to let him take the 116 pages of manuscript, and when he was told "no" he persisted. When he finally got the Lord's reluctant permission it was not for Martin Harris' benefit, but for Joseph's. Joseph was to learn a hard lesson about disregarding good advice from a superior Guide. (D&C 3: 1-8.) This comprehension of the harmony of the whole is what provoked Joseph to teach: "the nearer man approaches perfection, the clearer are his views, and the greater his enjoyments, till he has overcome the evils of his life and lost every desire for sin; and like the ancients, arrives at that point of faith where he is wrapped in the power and glory of his Maker, and is caught up to dwell with Him." (DHC 2: 8.)
Choose your teachers carefully. None of them will neglect to emphasize a virtue. However, without the whole of the Gospel in harmony in their own lives, they cannot bring it into harmony for you. Finding that harmony IS the great challenge in this lone and dreary world, filled as it is, with the philosophies of men mingled with scripture.