It is a disconcerting moment when your liberal conscience hits the buffers and you are consumed by pure rage and hatred for a stranger. I supposed that I had typically modern, moderate, evolved ideas about civilisation and justice; I support prison reform, believe in the possibility of rehabilitation, am glad to live in a society whose criminal justice system takes account of serious mental illness.

Yet when those beliefs come up against Josef Fritzl, I and many other women I talk to find that every ideal goes up like straw, destroyed in the heat of pure, unadulterated hatred.

Intellectually, I am glad he has had a trial and a defence lawyer to speak for him. Emotionally - and it is real emotion - I want him dead. No, worse than dead: tormented for life, not snugged down in some cosy mental hospital but imprisoned, humiliated, preferably flogged, confronted daily by what he did. I can raise no enthusiasm for the “suicide watch” he is on, and would blame his guards not one bit if they turned away to eat their sandwiches. Nor am I glad a psychiatrist has been standing by to cheer him up in the gaps during his trial.

I do not believe, as he would like us to, that the experience of watching the video evidence from his daughter was punishment enough, and made him realise “for the first time” what his “unfulfilled needs” forced - ha! forced! - him to do. I think that is a load of self-serving hooey.

I wish they had not allowed the evil old pig to hide his face behind that blue folder on the grounds that he was “embarrassed” by scrutiny from the press and public. Embarrassed, was he? Perhaps he feels that there was no embarrassment - let alone terror and humiliation - for the teenager he chained and raped in the clammy darkness of his vault, for the children born in squalor and forced to hear her repeated ordeals, or for the upstairs family who have had to learn about all this.

He pleaded guilty at last, in a plainly calculated attempt to end up in a relatively kindly hospital amid empathetic headlines saying “his world has collapsed”. I don't care if his world has collapsed: I hope he chokes, slowly, in the rubble. Lock him up, deny him everything, including understanding and psychiatrists. Josef Fritzl is the end, the limit, the death of hope.

I honour those who can think otherwise, and bear to treat him with common humanity. I could not. Even to write this makes me shake with fury and a kind of shame. But every normal attempt at understanding fails in his case, more than in any other. This was not a man driven to outbreaks of violence or lust by sudden urges, mental aberrations rooted in a childhood of extreme dehumanising misery. Resentful he may be of his mother (always blame the women) but all the evidence is that this is a sane man, a careful planner, an authoritarian husband and father with enough intelligence, skill and foresight to create a torture chamber, maintain it for 24 long years, and relax enough to present himself to the world as polite and hardworking, and to take holidays on a Thai beach while his daughter suffered torments of uncertainty for herself and the captive children.

Oh, he knew what he was doing: his plea that incest was “consensual” is the ultimate insult, a mental rape in its own right, given the victim's injuries and testimony of his perverse amusements. He has spoken of an “addiction that got out of control”, but that is evil nonsense, modish cant to save his neck.

An addiction that destroys the addict is perhaps excusable; one that brings indirect sorrow to a family is less so, but still understandable. To become “addicted” - for 24 years - to a highly organised torture of your own daughter is not. Nor can any personality problem justify wrecking the health and minds of three growing children - one for 19 years - in that same narrow oubliette.

Fritzl was not out of control. He was in it, too far in, revelling in control, a secret Satan. “I must have been crazy,” he says now. “What I did was not right.” No, Herr Fritzl, it was not. And the world hates you for it and always will.

Of course, there is much else to be said about this case; about the lackadaisical attitude of Austrian children's services, the downtrodden inadequacy of the wife, the secretive social culture of the country itself. There should be wide and sober reflection, too, on the dangers of a patriarchal culture - still extant in some communities in this country, if you consider “honour” killings - in which a father comes to believe he owns his children in the same sense he owns his socks.

Let all these things be discussed, let Austria reflect on whether it is indeed socially guilty. But in the end, it all comes down to Fritzl: the bad, bad, selfish man who stole his daughter's youth and motherhood, imperilled her life and sanity (she is heroic in her survival) and utterly disregarded the welfare and sanity of her children, including the group upstairs who now must come to terms with the horror their siblings underwent beneath their feet, year after year.

His “apology” in court was ludicrous, insulting, self-serving. If it promotes his children's sanity now to learn to forgive him, as in that Catholic country they may, so be it. I wish them well. But his only real achievement, diabolical beyond understanding, is his effect on those of us who thought of ourselves as liberal, merciful, believers in possible rehabilitation. Josef Fritzl has made himself impossible to pity.

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