At Duke, I had the privilege of taking I. B. Holley's intellectual history course my senior year. I remember the discussion he led of the impact of available contraceptives. His basic point was something like "Now we will see whether sexual morality really means anything, where the consequence of pregnancy is removed."
Of course, we were already seeing those consequences by the 1967-1968 academic year. I had a notion of contraceptives in high school, and learned that they were in active use among a couple of my peers during a trip our church youth group took to the World's Fair in NY in 1964. By my senior year at Duke, one of the brothers and his girl friend from East Campus had taken up living together in his dorm room in the basement of our fraternity's quad section. (During graduation week, I sang at their wedding! So marriage wasn't completely dead.) It was by then routine for unmarried student couples as a group to travel to Myrtle Beach for the weekend in the spring. Consequence-based sexual morality was already in full flight from the battlefield. In fact, the battle was over. It just took awhile for the news to spread.
Now, government provided contraceptives pretty much caps it off. In a related development, the approval of same-sex marriage affirms the triumph of childless relationships. It is left to some of the churches (and some ethicists, a few economists, psychologists, and sociologists, and at least one, once popular comedian) to promote the idea of "chastity in singleness and fidelity in marriage."
I don't recall Dr. Holley ever saying that Western Civilization as we know it depends on such morality. His purpose was to get us to think about the issue. We knew what he thought about it, however. (That was very important to me - what he thought. Still is.) But it takes a huge leap of the imagination for a person's conduct to be affected when short-term consequences are removed. That's why Dr. Holley taught the class and what we used to call a "liberal education" was so valuable: so that our minds could make those leaps.