While we are on the topic of the sexual revolution, Brad Wilcox has an informed and useful commentary in the Washington Post on the attempt by some of the old guard to normalise infidelity.

Wilcox, director of the National Marriage Project, points out that Americans are actually becoming less tolerant of marital infidelity:

In fact, notwithstanding the recent marital misbehavior of
athletes, actors, and politicians, public tolerance for marital
infidelity has fallen since the 1970s, with fully 79 percent of American adults now saying that infidelity is “always wrong.” Moreover, recent research from the National Marriage Project indicates
that infidelity has also declined in recent years to the point where
just 16 percent of married men and 10 percent of married women now
report that they have been unfaithful. So, clearly, in contemporary
America that vast majority of couples reject infidelity in theory and
practice.

However, sex advice columnist Dan Savage and some academics have told the New York Times that not everyone is "wired" for monogamy and that affairs may even be good for some marriages.

Wrong, says Wilcox, laying out five evidence-based reasons why what used to be called "open marriage" and is now called "swinging" is problematic for all concerned. Here is just one of them:

2. Monogamous, married sex is more likely to deliver long-lasting satisfaction than the quick thrill offered by infidelity. According to the renowned University of Chicago Sex Survey,
a “monogamous sexual partnership embedded in a formal marriage
evidently produces the greatest satisfaction and pleasure.” This study
found that both women and men like the emotional security that fidelity
affords, and are more likely to report that they are “anxious,”
“scared,” and “guilty” when they have had sex with multiple partners in
the last year.

You should read the other four.