“It is indeed better (as no one ever could deny) that men should be led to worship God by teaching, than that they should be driven to it by fear of punishment or pain; but it does not follow that because the former course produces the better men, therefore those who do not yield to it should be neglected. For many have found advantage (as we have proved, and are daily proving by actual experiment), in being first compelled by fear or pain, so that they might afterwards be influenced by teaching, or might follow out in act what they had already learned in word.” –Saint Augustine, Treatise on the Correction of the Donatists.
Side note: I can attest to this. It was fear that brought me back to the Church originally. Which in time has led to influence by teaching and love of Christ.