Here's the actual trend:

1)  1950 and before, such things weren't reported because of the culture and a complying media, but priests were just as active in abusing children.  The idea that there wasn't a lot of rape happening 1950s and before is without foundation.

2)  The reports from the 70s only seem higher than the past, but that's because those reporting were the subjects of the media's 1990s investigations.     

3)  The lessening of reports of priestly rape is wholly due to the effect of the media and the courts in influencing public opinion to make the church, finally, take action against errant priests.   The church would likely never have taken such action without this secular pressure.

Conclusion:  the notion that the hippie era make priests go sex crazy is a myth.