It's not for nothing that God routinely describes idolatry as "whoredom" and "adultery." If God is His people's husband by covenant, if we, the Church, are His Bride, bought at a price, then our looking to other gods is whoredom and our consorting with the idols of other gods is adultery.
And there is always correspondence between spiritual reality and physical. That's why it's so important that we don't separate the spiritual from the physical in our worship. If we say, "I'm worshipping on the inside," but our countenance never shows it or our posture never reveals it, the truth is we're not doing it on the inside. This is why we bow in confession--not that bowing makes it true, but because true repentance is lived out in every area of life, including the physical. The same is true of rejoicing.
Thus, when we are spiritually adulterous, spiritually promiscuous, whoring after other gods, we will be physically promiscuous and immoral as well. This is why idolatry walks hand-in-hand with sexual perversion and sexual immorality.
This is an iron spiritual law: where there is sexual perversion, where there is physical adultery, where there is sexual promiscuity and unfaithfulness, there is spiritual promiscuity and unfaithfulness as well. Without the spiritual adultery of idolatry, physical adultery cannot take place. Where there is sexual immorality--remember that the progression of sin in Romans 1 begins with rejection of God and turning to idols and advances from there into sexual sin--there is idolatry.
This means that we need to rethink what we consider the base sin at the core of pornography. We have tended to think of pornography as only a sexual sin. But at the core of pornography is the sin that is found whenever an image is worshipped: idolatry. Pornography is idolatry. It may also be sexual sin. But first it's the worship of an image, plain and simple. Pornography equals idolatry. Pornography is the modern term for the worship of Venus and Aphrodite and Artemis and all the love gods and fertility goddesses of the past. Past cultures had their sexually charged images, their lust idols with oversized genitalia and crudely sexual meanings or their sophisticated goddesses of love. So do we.
Here is the beauty of idolatry in the eyes of the idolater. It demands giving way to the flesh. It demands immorality. Our flesh wants to be sexually promiscuous and adulterous? Why how convenient: the idols of our gods call us to that as well.