He advanced the idea that the church was the custodian of an infallible system of doctrine, and that salvation was available only to those who would submit to its discipline. In the eyes of this great and good man, the church would be greatly blessed and greatly honored if she fulfilled the role outlined in The City of God. But after Augustine died, it was his idea that lived on, playing a vital role in the creation of the most oppressive religious system. But sacred history demonstrates that good men may be more dangerous than evil men. Even when a good man puts his mold on the work of God, nothing but evil will come of it.
Good men are often the more dangerous because their influence in religious things is greater.
Think of the great evil wrought by Gideon after God had used him mightily to deliver Israel from the Midianites. Instead of waiting for divine guidance, he began to plan for himself. The fact that he was a mighty man of valor, greatly favored of the Lord, made his departure from the truth the more dangerous. The people were led away from God by the very man who had once overthrown their idolatry. Think of John Calvin, the pious theologian of the Reformation.