Your assertion that spike was post-concillar is false. The peak was post-concillar, but the sharpest increases proportionally were in the late 50s and early 60s. By 1990, the rate had fallen below 1965 levels, even though few cases where the preist had died were reported. (Meaning any 1965 priest that didn't survive the next THIRTY-EIGHT years was not counted.)
So how can you blame the council for a crisis that was in full swing by the council? It's like trying to blame President George H W Bush for AIDS, or Ronald Reagen for early-80s recession.
You are just flat-out wrong. The John Jay study commissioned by the Bishops Conference and released by the National Review Board indicates a huge spike of reported sex abuse incidents concerning minors and clergy beginning with the early 60s and peaking in the mid-80s. There are many graphs that can be checked. The number of incidents during the 50s was relatively miniscule. The sharpest peak was in 1985 when the media began exposing the scandals. After this there is a gradual tapering-off in the 90s, but still a much higher number of incidents reported than in the 50s. There was one brief spike in 1960 with the election of the liberal John XXIII--which was probably why that pontiff issued the decree prohibiting gays from the priesthood, a proscription totally ignored with disastrous consequences. As for the 50s you can check the charts yourself. There were very few incidents. The study is available at the following site:
http://www.usccb.org/nrb/johnjaystudy/prev1.pdf
The above site is not to the charts I mentioned. Here is a better link:
http://johnjay.jjay.cuny.edu/churchstudy/_pdffiles/prev3.pdf