Kleinig, John W. Pastoral Letter on Porn.
The regular use of pornography for masturbation is a kind of sexual addiction. When Paul speaks about impurity and sexual greed as idolatry in Ephesians 5:3-7 and Colossians 3:5, he accurately describes how it works. It begins with sexual impurity, the defilement of our imagination by depictions of sexual intercourse that present naked bodies as idols for us to admire. Our fixation on these images arouses disordered desires and make us more and more greedy for sexual satisfaction from things that God has not given to us for our enjoyment. Yet they fail to satisfy us and serve only to feed our growing appetite for them…