Part of the Church’s immunity to reform stems from those who slander it. False accusations of homosexuality and homosexual abuse have also been a persistent tactic against the Church, from the Lollards to the Know-Nothings to the Stalinists. John Paul II, himself, according to George Weigel, was slow to realize the scope of the American crisis, because he had known of many false allegations made by the communists against the Catholics of Poland. (I would note that he was fantastically effective, nonetheless; the rate of sexual abuse in the US declined over 97% between 1980 and 1991.)
I once found at the very ground on which my apartment had been, had once stood a convent. One evening, roused by Protestant preachers, the townsfolk brutally murdered the entire convent. No-one was convicted.
http://en.wikipedia.org/wiki/Ursuline_Convent_Riots
Update: The entire convent was destroyed; I read where several of the nuns survived. The Wikipedia article makes no mention of the killings.
The old story about the boy crying “Wolf!” still applies.
Bizarre claim.