Question 137: Which is the seventh commandment?

Answer: The seventh commandment is, Thou shalt not commit adultery.

Question 138: What are the duties required in the seventh commandment?

Answer: The duties required in the seventh commandment are, chastity in body, mind, affections, words, and behavior; and the preservation of it in ourselves and others; watchfulness over the eyes and all the senses; temperance, keeping of chaste company, modesty in apparel; marriage by those that have not the gift of continency, conjugal love, and cohabitation; diligent labor in our callings; shunning all occasions of uncleanness, and resisting temptations thereunto.

Question 139: What are the sins forbidden in the seventh commandment?

Answer: The sins forbidden in the seventh commandment, besides the neglect of the duties required, are, adultery, fornication, rape, incest, sodomy, and all unnatural lusts; all unclean imaginations, thoughts, purposes, and affections;all corrupt or filthy communications, or listening thereunto; wanton looks, impudent or light behavior, immodest apparel; prohibiting of lawful, and dispensing with unlawful marriages; allowing, tolerating, keeping of stews, and resorting to them; entangling vows of single life, undue delay of marriage; having more wives or husbands than one at the same time; unjust divorce, or desertion; idleness, gluttony, drunkenness, unchaste company; lascivious songs, books, pictures, dancings, stage plays; and all other provocations to, or acts of uncleanness, either in ourselves or others. (Here)

"Lascivious songs, books, pictures, dancings, stage plays"? I'm sure that movies in which naked people rub their naked bodies against each other in simulation of sexual intercourse don't count.

I mean, it's not like you'd mind if you came home from work to find your spouse rubbing his naked body against someone else's since, after all, it's only a simulation.

If it were the real thing that would be something else.