If we can tolerate all the risqué ads on TV & billboards etc, then we can deal with some healthy truth. Israel would send its 'Head' into the secret place. If a priest would go behind the veil of flesh unclean and in broken covenant with God, this priest would produce his personal death. The glory could not come into contact with defilement. A priest could not casually come on in. He had to be in relationship and in covenant. He even needed to be circumcised as a sign of covenant and cleanliness as well as a public declaration of the condition of his heart. This in no way means we need to be circumcised in order to have sex with our spouse.
When a man enters into a woman's secret place and he is unclean in heart, out of relationship and not living in covenant with that woman, they will only produce death. Casual sex is a terrible injustice to the parties involved. Sex outside of covenant is wrong because intimacy without covenant is damaging to the spiritual cycle of life. We introduce into this natural realm the fruit of reckless abandonment, rather than mutual submission in covenant and in relationship.