Niebuhr thesis is being that group relations can never be as ethical as those, which characterize individual relations. So I think what he is trying to say is that as an individual you can have your own authentic opinion then compared to a group opinion. Gilkey locates Moral Man not only in its historical context but also in relationship with his later theological works, especially The Nature and Destiny of Man.
In Moral Man and Immoral Society, Niebuhr truly broke with this "social gospel" outlook, insisting that power is the principal ingredient in arbitrating the competing claims of nations, races, and social classes. According to Niebuhr, conflict and tension are permanent features of history. While social improvement is possible, the justice of this world is born in strife and is always provisional, fragmentary, and insecure.
Man, as a creature whose existence paradoxically combines spirit and matter, can sense his own "finitude and fragility" in the universe; annihilation and meaninglessness threaten all of his hopes, achievements, and affections.
Thus man is tempted to prideful assertions of his will that provide an illusion of control and meaning. While he can ease his anxiety and pretension through faith in God rather than self, that faith is always imperfect.
"Reason can sharpen ethical sensitivity and practice, but, ironically, it can also sharpen the capacity to rationalize selfishness and the will to power--and, doubly ironic, sometimes both at the same time"(22).
Individual is dealing with self-transcendent and nation is dealing with other nations. Or social classes with other social classes have little or no capacity for self-transcendence that is immoral society. According to Niebuhr nations and classes have limited understanding of the people they harm by their unjust self-assertion.
However, they lack appreciation for the often complicated laws and institutions through which such injustice is...