So the downfall of the Catholic church in Scotland didn't occur at the hands of the Orangemen or the secular humanists of the church's vivid imagination. All of the most grievous wounds it has suffered have turned out to be self-inflicted. The catalogue of sexual abuse by hundreds of priests stretching back decades; the sexual bullying of priests by its own cardinal; the cover-ups and intimidation of witnesses and victims – it didn't need the assistance of any external agency to bring about the moral catastrophe that currently engulfs it.

The single beacon in this, the Scottish church's darkest period, was provided by the most unlikely source. One of the victims of the sex abuse by priests at Fort Augustus Abbey School broke his anonymity last Sunday night and agreed to be interviewed on television. His words gave us a sense of the anger and humiliation he still felt more than 40 years after his torment. Yet he also possessed a dignity, courage and wisdom that has been entirely missing from the Scottish Catholic church and from Rome since the lid began to be lifted on this cesspit earlier this year.

This man was not impressed by the apology offered by the bishop of Aberdeen, Hugh Gilbert, pointing out, correctly, that public opinion and widespread revulsion following BBC Scotland's excellent investigation into abuse at Fort Augustus the previous week had dragged it from the church.

For any confession to be considered sincere and authentic, this brave man also pointed out, it has to be accompanied by "a firm purpose of amendment". Nothing, though, in any of what has passed for a response from the church, has contained anything remotely like "a firm purpose of amendment".

For this to happen, either the pope or the Scottish hierarchy first have to answer the following questions: which bishops and archbishops knew about some of this and allowed it to continue unchecked; how does an obviously flawed and sexually aggressive individual such as Keith Patrick O'Brien get to become cardinal, and precisely how do you intend to reform the behaviour and attitudes of the clergy and hierarchy in the wake of these scandals?

There are still Catholics out there, some of whom the media like to call "influential", who remain in denial about what this all means. They think that this will all simply evaporate. So let me spell it out for them. The Catholic church in Scotland has, by its behaviour and absence of leadership in these matters, renounced all right to comment on matters of ethics and morals in the wider community.

For how long that remains the case will rest on how quickly a proper inquiry into the running of the church over the past 50 years is instituted, and what material and practical steps will be taken in its wake. It will also rest on the length and sincerity of the period of repentance that the church needs to undertake for its failures and errors.

When monsignor Leo Cushley's elevation to the post of archbishop of St Andrew's and Edinburgh was announced last month, I couldn't help noticing, once more, how grand are the house and gardens at St Bennet's, his new official residence. On the open market, such an opulent domicile would surely fetch millions. We have also allowed Mario Conti, the recently retired archbishop of Glasgow, to bide in a gorgeous £750,000 property in one of the leafier suburbs of the city's south side. I'm not sure where our working archbishop, Philip Tartaglia, currently stays, though I'll hazard a guess that it won't be too shabby, either. In fact, if you were to add together the value of all of the gilded properties belonging to the princes of the church (both serving and retired) the sum total would be at least £5m.

The bishops have no need to be housed in leafy, affluent luxury. They are all single men who are working to serve their church and who are beginning the task of repairing it. I'm certain that they could each carry out these functions in nice but unostentatious apartments in the midst of the communities they serve.

Many parish priests, too, reside in homes that are the largest properties in their neighbourhoods. Many of these were built to accommodate several priests living in the community. Those days have gone for good, though, as recruitment to the Catholic priesthood has collapsed. For what Catholic parents now would seriously consider allowing one of their children to train for the priesthood? Some priests will argue that, as their houses are attached to the church, selling them off would be impractical. In these cases, what could be better than deploying them as shelters for the homeless? "Come unto me all ye that labour and are heavy laden and I will give you rest."

Catholics in Scotland are disproportionately poorer than other social groupings. More Catholics are in prison than there ought, proportionally, to be. Since famine and persecution drove them from Ireland, they have long faced stiff economic challenges and have supported the church while coping with extreme personal hardship.

The sum raised by the wholesale selling off of episcopal residences and parish houses would be a pretty one indeed, and could be used to support the establishment of viable credit unions, as proposed by the Anglicans and the Church of Scotland. In this way, the church would be helping to lift its poorest brothers and sisters out of the clutches of the evil payday loan firms. And it would be an appropriate and material act of contrition for the sins it has committed against its own. If the Catholic church in Scotland refuses to deal properly with this, then it does not deserve to exist.

And so, four and a half centuries after the Protestant Reformation, it may be time to join it.• This article will be opened for comments on Sunday morning