What is the rational explanation about why pornography is wrong?
Pornography is to stimulate sexually, by experiencing strange flesh. The idea of pornography is to imagine sexual activity with that mate. Then it is addictive, to seek out more experiences, because different mates invoke different pleasures.
This then causes us to begin looking at the people around us with fantasy, in search of new pleasures. This is a self-gratifying view of people.
As a result, people do not feel valued for who they are, but for how they look. There is a false perception of value associated to appearance, that can cause anxiety in various ways. Many people will wrongly diagnose the lack of respect as owing to their sexual appearance, when actually sexual appeal does not produce the respect they need.
Fantasy is also only a few steps from adultery, so where someone is engaging in pornography and they lust for a colleague or friend etc, there is already an interest and there is potential for temptation when an opportunity comes to act on it. Proverbs 6:34.
Lust is a mortal sin. Sin and love are opposites. Where sin is motivated by self interests, love is motivated in the interests of others. So when we are conditioned to look at people as a source of sexual stimulation, that is to see them as a thing for our gratification. Whereas to recognise them for their person, to look past their sexual appearance, we are able to engage with them in full respect of who they are as a person.
Furthermore, seeing that lust is sin, it is selfishness, it produces fruits of the flesh that are at odds with the fruits of the spirit.
Therefore, when someone is engaging in a lustful lifestyle, as for example pornography or sexual fantasy (as the TV encourages), then that one is grieving and quenching The Holy Spirit by cultivating fruits of the flesh that are at odds with the fruits of the spirit.
Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ; as obedient children, not conforming yourselves to the former lusts, as in your ignorance; but as He who called you is holy, you also be holy in all your conduct, because it is written, “Be holy, for I am holy.”
1 Peter 1:13-16
Flee whoring. Every sin that a man commits is outside the body, but he who commits whoring sins against his own body. Or do you not know that your body is the dwelling place of The Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought with a price, therefore honour God in your body and your spirit, which are of God.
1 Corinthians 6:18-20