I would give them an attitude of suspicion toward everyone outside their circle of like-minded friends. They would waste endless effort attacking sincere Christ-followers from other theological traditions, while tolerating sin and error in their own circle. I would cultivate in them an unteachable attitude, so they would regard the wisdom passed down to them by spiritual and intellectual giants of little worth in comparison to their own unqualified opinions. I would persuade them that accountability is only for the weak, and that God’s approval of their lifestyles can be proven by emotional experiences. Being a Christian would be more about fitting in with a religious subculture than conforming to God’s will. As a result, fellow believers who dare to challenge them would be quickly expelled as outsiders; guilty of “sowing discord” and those who don’t rock the boat would live comfortably unchallenged. I would create a set of pet issues, sins that deserve special attention, so that these Christians can spend their days self righteous in the stand they’ve taken against sin, when in reality they’ve only been preaching against other people’s sins, and ignoring their own.
Finally, I would inextricably infuse their Christianity with political ideology, then slowly remove the Christianity until all that was left was religious political fervor. They would come to believe that the ability of the church to accomplish the Great Commission, is tied to the success of one political ideology, and they would never again doubt that God wants their favorite politician in power. I would convince them that God’s plan for the church is that they win elections and pass laws at whatever cost. I would persuade them that fervent patriotism is a suitable substitute for cumbersome righteousness, as long as they make sure to oppose abortion and gay marriage. I would goad them to label anyone who tries to return them to God’s Word, an out of touch holier-than-thou Pharisee. I would convince them to discard Biblical thinking as being too idealistic, and to replace it with comfortable practicality. They would never know the difference, because the Bible they read, and indeed the Christ that they follow always perfectly reflects their own biases, assumptions, and perspective.
In other words, if I were the Devil, I would keep doing what I am doing now.