Pardon my ignorance, but that passage makes absolutely so sense to me. Is it saying that one should not take steps to save the lives of suffering people, because when those people die God with receive them upon himself, in glory? I'm confused.
There are several aspects to this that need to be considered. First, it bears mention that the whole system is designed to be temporary; death ends all suffering. So there is a limit to how suffering can be caused by evil designs.
Secondly, in the parable of the wheat and tares, we are taught that the premature destruction of the wicked hurts the righteous. God waits until either all the fruit is ripe, or until it can be shown that there will be no fruit. Righteousness may actually need a somewhat adverse environment to properly grow. How many people become so disgusted of wickedness that they choose to be righteous?
Third, God lets mankind govern themselves. With rare exception, he doesn't interfere in what he considers to be our own responsibility. He even let his own son be tortured, rather than interfere.
Forth, God lets men choose how they will act, before judging them. A crime has to be committed before the punishment is just.
Amulek thought that he was in a position to call upon God to end the suffering of the women and children, but Alma was constrained to let the wickedness take its course, so that the ultimate punishment would be just.
One consideration is whether the people have been taught the truth of the gospel and subsequently rejected it. God is far more tolerant of people who sin in ignorance, perpetuating societal ills because of their false traditions. Another consideration is whether it is the act of one man, or the act of an entire society. With Sodom and Gomorrah, just the presence of ten righteous people would have averted disaster. He doesn't seem to micromanage; he waits for a society to ripen in wickedness before passing judgement. Until that happens, many people will suffer at the hands of the wicked, and societies are left alone to govern themselves.
God certainly does make exceptions from time to time, particularly when it comes to missionary work. He wants everyone to have a chance to hear the gospel, either in this life, or in the spirit world, but preferably in this life. He works through subordinates, so there is a manpower issue.