From Erich Fromm's The Art of Being:
"The basis for any approach to self-transformation is an ever-increasing awareness of reality and the shedding of illusions. Illusions contaminate even the most wonderful-sounding teaching to make it poisonous. I am not referring here to possible errors in the teaching. The Buddha's teachings are not contaminated because one does not believe that transmigration exists, nor is the biblical text contaminated because it contrasts with the more realistic knowledge of the history of earth and the evolution of man. There are, however, intrinsic untruths and deceptions that do contaminate teaching, such as announcing that great results can be achieved without effort, or that the craving for fame can go together with egolessness, or that methods of mass suggestion are compatible with independence.
"To be naive and easily deceived is impermissible, today more than ever, when the prevailing untruths may lead to a catastrophe because they blind people to real dangers and real possibilities.
"The 'realists' believe, of those who strive for kindness, that these latter mean well but that they are ingenuous, full of illusions--briefly, fools. And they are not entirely wrong. Many of those who abhor violence, hate, and selfishness are naive. They need their belief in everyone's innate 'goodness' in order to sustain that belief. Their faith is not strong enough to believe in the fertile possibilities of man without shutting their eyes to the ugliness and viciousness of individuals and groups. As long as they do so, their attempts to achieve an optimum of well-being must fail; any intense disappointment will convince them that they were wrong or will drive them into a depression, because they do not then know what to believe.
"Faith in life, in oneself, in others must be built on the hard rock of realism; that is to say, on the capacity to see evil where it is, to see swindle, destructiveness, and selfishness not only when they are obvious but in their many disguises and rationalizations. Indeed, faith, love, and hope must go together with such a passion for seeing reality in all its nakedness that the outsider would be prone to call the attitude 'cynicism.' And cynical it is, when we mean by it the refusal to be taken in by the sweet and plausible lies that cover almost everything that is said and believed. But this kind of cynicism is not cynicism; it is uncompromisingly critical, a refusal to play the game in a system of deception. Meister Eckhart expressed this briefly when he said...'He does not deceive but he is not deceived.'
"Indeed, neither the Buddha, nor the Prophets, nor Jesus, nor Eckhart, nor Spinoza, nor Marx, nor Schweitzer were 'softies.' On the contrary, they were hardheaded realists and most of them were persecuted and maligned not because they preached virtue but because they spoke truth. They did not respect power, titles, or fame, and they knew that the emperor was naked; and they knew that power can kill the 'truth-sayers.'"