Timothy Keller in his book ‘The Reason for God’ wrote:
Perhaps the biggest deterrent to Christianity for the average person is not so much violence and warfare but the shadow of fanaticism. Many non-believers have friends or relatives who have become “born again” and seem to have gone off the deep end. They soon begin to express loudly their disapproval of various groups and sectors of our society—especially movies and television, the Democratic party, homosexuals, evolutionists, activist judges, members of other religions, and the values in public schools. When arguing for the truth of their faith they often appear intolerant and self-righteous. This is what many people would call fanaticism.
Many people try to understand Christians along a spectrum from “nominalism” at one end to “fanaticism” at the other. A nominal Christian is someone who is Christian in name only, who does not practice it and perhaps barely believes it. A fanatic is someone who is thought to over-believe and over-practice Christianity. In this schematic, the best kind of Christian would be someone in the middle, someone who doesn’t go all the way with it, who believes it but is not devoted to it. The problem to this approach is that it assumes that the Christian faith is basically a form of moral improvement. Intense Christians would then be intense moralists or, as they were called in Jesus’s time Pharisees. Pharisaic people assume they are right with God because of their moral behavior and right doctrine. This leads naturally to feelings of superiority to those who do not share their religiosity and from there to various forms of abuse, exclusion and oppression. This is the essence of what we think of as fanaticism.
What if, however, the essence of Christianity is salvation by grace, salvation not because of what we do but because of what Christ has done for us? Belief that you are accepted by God by sheer grace is profoundly humbling. The people who are fanatics then, are so not because they are too committed to the gospel but because they’re not committed enough.
Think of people you consider fanatical. They’re overbearing, self-righteous, opinionated, insensitive, and harsh. Why? It’s not because they are too Christian but because they are not Christian enough. They are fanatically zealous and courageous, but they are not fanatically humble, sensitive, loving, empathetic, forgiving, or understanding—as Christ was. Because they think of Christianity as a self improvement program they emulate the Jesus of the whips in the temple, but not the Jesus who said, “Let him who is without sin cast the first stone” (John 8:7). What strikes us as overly fanatical is actually a failure to be fully committed to Christ and his gospel. ~Timothy Keller, The Reason for God: New York, New York: Penguin Books, 2008, 2016), 58-59
