Archbishop Patrick Kelly told the BBC that the work of other organisations dealing with children should be examined.
He said that most child abuse "occurs within families".
The Pope begins a four-day visit on Thursday to deliver open-air masses to millions of Catholics.
Archbishop Kelly said: "It's also worth asking similar groups who worked with young people what were they doing in those same years?
"Other groups were working with young people and we've found that the question of child abuse, above all, occurs within families - You know that as a fact.
"According to what others were doing at the same time, I'm afraid we were so ignorant we did not know about the addictive nature [of paedophiles]."
He said that Pope Benedict XVI, who has faced allegations of delaying Church action against exposing abuser priests to prosecution, has acted firmly.
The Archbishop said: "Nobody has been so rigorous in dealing with that terrible issue as he has. He has insisted that procedures are in place.
"If people can give [the Pope] a fair hearing in the coming days, I think they'll be enlightened, encouraged and given a great sense of joy."
SIC: BBC/UK