"The wife's body does not belong to her alone but also to her husband. In the same way, the husband's body does not belong to him alone but also to his wife." 1 Cor 7:4
This is a great nugget of wisdom which deftly encapsulates what I think is intuitive, even in our wayward culture, about sexual morality. Think about the romantic movies you have seen. Even if someone (hero or heroine) is leaving their spouse (i.e. in an adulterous relationship, giving away what belongs to the forsaken spouse) for someone else, some twist of plot, some gimmick will appear to make this after all, ok. Frequently, the forsaken spouse, good, evil, or whatever, will conveniently die so that the plot is not embarrassed by his presence. (I use 'his' here in the correct generic sense.) Also if an unmarried pair of hero and heroine copulate in the process of the plot, they will frequently be married by the end of the movie, which somehow legitimizes their previous dalliance. How convenient. How much nicer for the viewers. But I think that Hollywood here, is not playing to the vestiges of a weakening Christian influence. I think that they are unconsciously paying lip service to an underlying feeling that straying from the reality as stated above by Paul, is distasteful, if not deeply offensive, to all.