Let me reverse your question and ask it this way: What exactly is right with pornography? The answer is simple: absolutely nothing. It is a total perversion of one of God’s greatest gifts to us—the gift of sexual intimacy between a husband and wife.
I could answer your question in many ways, of course, but in this limited space let me point out two reasons why pornography is wrong. First, it’s wrong because of what it does to us. It appeals only to our self-centered, sinful, pleasure-seeking nature, and the more we get involved with it, the more we feed that nature and become captives to it. The Bible says, “The sinful nature desires what is contrary to the Spirit. … They are in conflict with each other” (Galatians 5:17).
Pornography is also wrong because of what it does to others. It treats others not as people but as objects, as playthings for our own selfish gratification. In other words, lust replaces love and that is wrong. This, incidentally, is why marriages based only on physical attraction seldom last.
Pray for your friend, not only that he will be freed from his captivity to pornography, but that he will turn his life over to Christ. Only Christ can forgive our sins, and only He can fill our lives with true joy and peace. Is your life committed to Him?