Gail Collins writes about the uneasy relationship between social conservatives and contraception. She cites two arguments that social conservatives make about contraception: the first relies on incorrect biology and the second reflects uneasiness with casual sex.
Collins spends more time on the incorrect biology argument, but I think that the social conservatives are more motivated by their unease with casual sex. The incorrect biology is not literally true in any way, but social conservatives may believe that the biology is metaphorically true. That is, many forces within the modern world are inhibiting committed relationships and family formation, and they hypothesize that one of the forces is contraception, which is a logical fallacy, but the emotional argument is understandable.
Social conservatives are terribly troubled by the state of modern sexual ethics, or the lack thereof. Their nostalgia is to some extent false: premarital sex and casual sex were not invented with the birth control pill, and the decline of marriage is explained by a myriad of social, economic, and demographic factors.
Nonetheless, their argument has a real kernel of truth that few deal with because it violates third wave feminism: casual sex is more common than it used to be, and all the research I'm aware of finds that casual sex has more negatives than positives (click on the casual sex label for my earlier summaries of that research).
Casual sex occurs between closed doors, both liberals and conservatives have casual sex, and I know of no policy that would decrease casual sex. Given its murky origins, it's not surprising that social conservatives are indiscriminate in the policies and theories that they scapegoat to explain casual sex. Sex education, family planning, emergency contraception, abortion, and Arnett's theory of emerging adulthood do not cause casual sex, and casual sex probably does not inhibit family formation. Social conservatives just cannot think of better explanations, especially given the relative paucity of research on casual sex. Liberals fear that attacks on casual sex are disguised attacks on reproductive rights, rather than seeing that for many the opposite is true: casual sex is the enemy, and reproductive rights are the scapegoat.
And so we have these repeated battles that really all stem from the same thing: unease with casual sex and delayed family formation.
Most people having this dialogue are married, and most married people have long been insulated from the world of singles and their sexual decisions. Instead, they take sides based on their other political beliefs.
The married social conservatives believe that casual sex comes from liberals, not realizing how much exists organically among conservatives and how many liberals have wholesome sexual ethics and are eager to marry. The married liberals believe that casual sex does no harm as long as both the sex and its casualness are consensual, as if such consent were truly possible. My understanding of the qualitative research (Bogle's Hooking Up) is that women may freely consent to casual sex only within limited circumstances (e.g., experimentation), but see it as second best outside those circumstances; conversely, women create the circumstances that enable casual sex by discounting many men, artificially narrowing their dating pool, giving more power to the few men considered "good catches."
Both married liberals and conservatives have apparently forgotten, or maybe they never experienced, the dating market that makes all of these issues so complicated. We can agree on one thing: most people want to get married and have extremely high expectations for marriage, but the path to marriage is murky for myriad reasons. Until we know otherwise, probably the best we can do is practice good sexual ethics and help individuals wherever we can.
At a policy level, the marriage and family formation research indicates that economic factors inhibit marriage among lower income groups, and the decline of unions, widening income inequality, and reduction in good jobs are likely responsible. If we invested the trillions of dollars needed to upgrade our infrastructure from a D to a B, providing jobs for lower income groups, that could help the country both economically (e.g., improved productivity due to reduction in accidents and water main breaks) and socially (by giving income and good jobs to (mostly) men, some of whom would marry their female companions.)