Os Guinness on Bad Faith
In modern times the charge of "bad faith" was raised by the French existentialists but is more widely associated with Marxist and Freudian attacks on religion — religion for Marx was the "opium of the people" and for Freud a "projection." Needless to say, the germ of the charge is far older and wider. "Fear made the gods," wrote Lucretius as a first-century B.C. Roman. Or as Henrik Ibsen remarked as a nineteenth-century Norwegian, "Take away the life-lie from the average man and you take away his happiness."
... There are several possible responses to this charge, such as those who wield it are rarely courageous enough to turn it on their own beliefs, the very charge is itself the biblical critique of idols, and so on. But at the end of the day, there is no answer without one: Those who put their faith in God do so for all sorts of good reasons, but the very best reason is that they are finally, utterly, and incontrovertibly convinced that the faith in which they put their confidence is true.