Archbishop Mancini's cry of anguish expresses how many of us feel. The scandal of Bishop Lahey's conduct is surely devastating. With God's grace perhaps it will be purifying too.
There are three principal reactions to news like this. One hears first from the anti-Catholics, more numerous than one might think and certainly vocal, who delight in the sins of Catholics. Those who would tell lies about the Church certainly will not blanch from telling damaging truths. It is embarrassing to have sins shouted from the rooftops, but the shouting and derision are only secondary to our own shame.
Second, one hears from the putative reformers, both within and without the Church, who consider every difficulty -- parish amalgamation, school closing, sexual scandal, financial crisis -- to be an opportune time for the Catholic Church to change her teachings. If only we had married priests or taught differently about sexual morality or modified our internal governance, then presumably everything would be better. In short, Catholics would have fewer problems if they were more like Protestants. There are serious doctrinal differences between say, Catholics and Anglicans or the United Church, but sinfulness is a shared part of the human condition. Catholic scandals get more attention than others, but the problems we have are not absent elsewhere, in the Church or society at large.
Third, one hears from those, again both Catholics and non-Catholics, who simply wonder about whether this is ever going to stop. The short answer is no -- there will always be priests and lay leaders who will betray the trust put in them. The longer answer is that those betrayals are growing fewer and being punished more readily. Catholics have learned, at the cost of the great pain and suffering of many innocents, how to better confront this evil behaviour.