In his stimulating The Pretenses of Loyalty, John Perry conveys a seminal moment in John Rawls’ life from autobiographical comments:
To the extent that Christianity is taken seriously, I came to think it could have deleterious effects on one’s character. Christianity is a solitary religion: each is saved or damned individually, and we naturally focus on our own salvation to the point where nothing else seems to matter. Whereas actually … our own individual soul and its salvation are hardly important for the larger picture of civilized life, and often we have to recognize this. Thus, how important is it that I be saved compared to risking my life to assassinate Hitler, had I the chance? It’s not important at all. 
Rawls give this as a reason for his own departure from the faith, and as an instance of a peculiarly moralistic reason for leaving, it is probably not the first time someone has turned from loyalty to Christ ostensibly for this cause. Those who tend to put the highest good in a political ideal will always find it psychologically painful to honor it less than Christ.
And it’s not as if one cannot see the surface plausibility to the objection. Decent people react negatively to selfishness, and it seems wildly egoistic to sacrifice the lives of millions for one’s own private good. But in fact this construal of the situation is a trick of the light, as Rawls’ description of the situation makes a number of theologically false assumptions.
The second is to construe the choice of one’s own salvation as merely a self-interested act. But for Christianity, divine condemnation is originally merited because a person places a created good above the infinite good, that is, God himself. Furthermore, from a Calvinist point of view, one cannot lose salvation by a mere sin because one cannot lose salvation at all. Insofar as biblical warnings express a hypothetical possibility of the regenerate finally falling from grace, it is again not for a mere sin. Rather, it happens because of a fundamental and permanent turning from loyalty to Christ. It would only be as an expression of such a turn that the act Rawls contemplates could imperil one’s salvation, per impossible. Regardless, the main problem with Rawls’ construal of the situation is that it subtly elides the presence of God as the highest good for human beings.
The third mistaken assumption is this: Rawls description of the situation basically assumes God as the classical Christian tradition conceives of him, does not exist. When one acknowledges that God does exist, it breaks the appearance of the iron necessity of a foreseen evil that follows from an intended good. If one must choose loyalty to God in a situation where one foresees an unwanted evil will happen as a result, the existence of God always provides a confounding factor. The person in that situation knows that God could prevent the evil, and hopes that he will. This affects the morality of the person’s action.
And God’s nature explains why it makes sense to obey him above all else. That is, since he is Goodness and Being itself, the person who wishes to do what is good will always seek him as their ultimate end, and it will never be morally necessary to disobey him. Anselm explains this point in Cur Deus Homo XXI:
Anselm.. Suppose that you did not owe any of those things which you have brought up as possible payment for your sin, let us inquire whether they can satisfy for a sin so small as one look contrary to the will of God.
Boso. Did I not hear you question the thing, I should suppose that a single repentant feeling on my part would blot out this sin.
Anselm.. You have not as yet estimated the great burden of sin.
Boso. Show it me then.
Anselm.. If you should find yourself in the sight of God, and one said to you: “Look thither;” and God, on the other hand, should say: “It is not my will that you should look;” ask your own heart what there is in all existing things which would make it right for you to give that look contrary to the will of God.
Boso. I can find no motive which would make it right; unless, indeed I am so situated as to make it necessary for me either to do this, or some greater sin.
Anselm.. Put away all such necessity, and ask with regard to this sin only whether you can do it even for your own salvation.
Boso. I see plainly that I cannot.
Anselm.. Not to detain you too long; what if it were necessary either that the whole universe, except God himself, should perish and fall back into nothing, or else that you should do so small a thing against the will of God?
Boso. When I consider the action itself, it appears very slight; but when I view it as contrary to the will of God, I know of nothing so grievous, and of no loss that will compare with it; but sometimes we oppose another’s will without blame in order to preserve his property, so that afterwards he is glad that we opposed him.
Anselm.. This is in the case of man, who often does not know what is useful for him, or cannot make up his loss; but God is in want of nothing, and, should all things perish, can restore them as easily as he created them.
Boso. I must confess that I ought not to oppose the will of God even to preserve the whole creation.
Anselm.. What if there were more worlds as full of beings as this?
Boso. Were they increased to an infinite extent, and held before me in like manner, my reply would be the same.
Anselm.. You cannot answer more correctly… .
The bolded portion provides the ultimate truth that undermines Rawls’ argument. Because God is the source of all things, and can restore everything, obedience to him is never simply sacrificing a good, because God is always capable of protecting and restoring it.
Aside from the political theological question of resistance, the basic problem underlying Rawls’ reasoning is this: he assumes God does not exist as part of his tacit argument for disbelieving in God’s existence. If God does exist then the moral situation is radically different from the way he describes it. We do not have to choose between preserving some fragile good and obeying God, because ultimately in every moment we have to do with God, and God can preserve any good he wishes. We, however, cannot live lives of moral excellence if we irrationally rank the Creator as a lower good than his creation.