In Friday's Washington Times, Frank Kacer wrote a piece entitled, "Sexual Impurity and the Corruption of Our Nation's Soul". I commend it to your reading for I think he makes important points. Many of us see that the acceptance of contraception paved the way for the acceptance of abortion. Mr. Kacer touches upon some factors that made contraception appealing to the less-principled citizenry.
He states that prior to the sixties our nation held onto a "thin veneer of sexual propriety". Therein lies the problem; sexual propriety was merely a thin veneer. In some cases it was so transparent as to be non-existent. I would hold that by and large, Americans lost sight of the eternal things and sought only to enjoy "the good life". Gradually, with less emphasis on seeking after the kingdom of God first, people became slowly corrupted and compromised.
Those people included Catholics - and Catholic clergy. By then, young priests who would later act out as homosexual pederasts were in place; some, like Father Hesburgh, occupied places of great influence. They failed to reach out to the Protestants to bring them back to the One True Church. Instead of the Catholics influencing the worldly culture, they allowed the worldly culture to influence them.
In partial answer to Kacer's question, "Can the slippery slope be stopped?", I'll venture to say not, unless the Catholics wake up and start acting like Roman Catholics and not some "am-church" counterfeit.