"For this is the will of God, your sanctification; that is, that you abstain from sexual immorality; that each of you know how to possess his own vessel in sanctification and honor, not in lustful passion, like the Gentiles who do not know God" (I Thessalonians 4:3-5).
“Therefore consider the members of your earthly body as dead to immorality, impurity, passion, evil desire, and greed, which amounts to idolatry. For it is because of these things that the wrath of God will come upon the sons of disobedience, and in them you also once walked, when you were living in them” (Colossians 3:5-7).
"But I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart" (Matthew 5:28).
Almost everyone realizes pornography is wrong. That is why they hide their viewing of it, but exactly what is wrong and what damage it causes is difficult for some people, especially young people, to grasp.