Jonathan Zimmerman teaches history and education at New York University. He is writing a history of sex education around the world.

In 1968, the prominent anthropologist Ashley Montagu published a brief article in praise of a revolutionary new technology: the birth control pill. “In its effects I believe that the pill ranks in importance with the discovery of fire,” Mr. Montagu wrote.

The pill would emancipate women to make their own sexual decisions, Montagu predicted; at the same time, it would eliminate the “exploitative attitude toward the female” among American men.

He was half-right. Although the soon-to-be-capitalized “Pill” gave women new freedoms, it also threatened a longtime male privilege: the sexual double standard. And traditional men weren’t going to let that go without a fight.

That’s the only way to understand conservative talk-show host Rush Limbaugh’s remarks last week about Georgetown Law School student Sandra Fluke, who had testified before Congress in support of President Obama’s policy requiring health insurance plans to cover contraception....

That’s why so many men fought for over a century against birth control, which remained illegal or highly restricted in many states until the 1960s. “Fear of conception has been an important factor in the virtue of many unmarried girls,” argued one physician in 1917. Take away that worry, he added, and single women could do anything they wanted.

It’s also why the American Birth Control League changed its name to “Planned Parenthood” in 1942. Conjuring marriage and family, the new title reassured critics who feared contraception gave too much sexual freedom to the unwed....