Pornography seems more disgusting than other evils. Some would argue that looking at the naked human body is not evil, because God made it beautiful, and Adam and Eve were naked in the garden. However, that was before sin entered the picture. What we look at does affect us spiritually - and can cause us to sin. The sin takes place even before the action is executed.
Scripture gives many examples of men being enticed by the sight of a woman.
Shechem saw the woman before he raped her. David saw the woman bathing before he had sex with her. Judah saw the harlot before he had sex with her. It was the same for Samson, etc. So David sent and inquired about the woman.