In 1962 the Vatican issued a secret letter of instruction to all Cardinals and Bishops. under the seal of Pope John XXIII, on how to handle accusations of "solicitation" (sexual misconduct) against Catholic clergy. The letter was published by the British press in 1993, and a copy of the original letter can be read here. The original 1993 Guardian newspaper article about the letter can be read here. Note that lawyers for the Curia do not deny that this letter was written, nor did they deny that the published copy was authentic, though they tried at the time of its publication to argue that it was taken out of context. In 2001 the Curia sent an additional letter to all Catholic Bishops reminding them that the 1962 letter was still in force. That letter was signed by then-Cardinal Ratzinger, the current Pope.
The key paragraphs are outlined in blue. In essence they enjoin everyone involved in such cases - accusers, witnesses, victims, judges - to take vows of perpetual silence under pain of excommunication. It seems to me that is pretty conclusive proof of an organized conspiracy to hide criminal behavior -- remember, sexually molesting underage children is a serious criminal offense. Enjoining everyone, including victims, to silence effectively prevents anyone from reporting the matter to the police for criminal prosecution.