This culture is now so ingrained that it is very hard to talk about it without seeming callous and cruel, and feeling sunk in guilt. I found myself in the horrible situation this week of having upset Sara Payne, a woman whose daughter, Sarah, was murdered in the most unimaginably evil way a few years ago. I am opposed to her campaign - picked up by the News of the World - to imitate America's Megan's law, which discloses the names and addresses of paedophiles to their neighbours. I argue, on the basis of all the available evidence, that shunning and shaming released paedophiles makes them more likely to relapse and rape another child, while tightly integrating them into support networks makes them less likely to reoffend.
Payne said this view "shocked and disgusted" her, and was "an insult to Megan [who was also murdered by a paedophile] and all the good work done by her parents in protecting children". When you are accused by a grieving mother of insulting murdered children, you would have to be a monster not to pause. But increasingly, our public debate withers and dies in that pause. The grief has spoken; end of argument.
This inability to have a serious discussion of Megan's law is only one small symptom. Grief politics has spread over Britain like black tar over the past decade. Look, for example, at the handful of parents who became convinced in the 1990s that their children had been made autistic by the MMR vaccine. They held up Dr Andrew Wakefield as their Gallileo, the only scientist to speak the truth against the wicked medical establishment. The fact that Wakefield had no reliable scientific evidence at all - and is now being investigated for professional misconduct - did not stop them.
Of course, it's not hard to empathise with these parents. Their campaign gave their grief meaning. If real political change came from their child's disability, it would mean their loss was not for nothing. It is harder to understand why their views were taken seriously and amplified by the right-wing press, who used their grief to persuade hundreds of thousands of parents not to use the MMR vaccine. The result? We are facing a measles epidemic, and dozens of children may die. Privileging pain over reason has, it turns out, led to a disaster.
This refusal to think about consequences - the decision to take grief as a full stop to any controversy - was recently epitomised by the New York Times columnist Maureen Dowd. She said nobody should try to answer Cindy Sheehan - a woman whose son Casey was murdered by insurgents in Iraq, and who now wants full troop withdrawal - because losing a child gives her "absolute moral authority".
As it happens, I agree with Sheehan that we need rapid withdrawal from Iraq, because a majority of Iraqis want us out now. (Only 1 per cent look to the multinational forces in Iraq to enhance their security, according to the latest poll.) But why does Sheehan's personal grief make that case stronger? Other people who lost children in Iraq have reacted by saying they believe the US should "nuke Baghdad". Does that deranged demand have "absolute moral authority" too? Grief does not necessarily overlap with being right, and it often militates against even being coherent.
And yet I understand the temptations of grief politics. When a grieving parent supports your cause, it is very hard not to pick them up and use them as a handy rhetorical device to silence critics. In arguing for, say, tougher gun laws, it's hard to resist smearing the tears of the Dunblane parents into your opponents' faces.
Recently I was arguing against Lembit Opik, the Liberal Democrats MP, about speed cameras, and I began to wax lyrical about the parents I have met whose kids were killed by Clarkson-style speedophiles. "How could you look them in the face and argue against speed cameras?" I asked, a lazy, hazy act of moral blackmail in place of the far better reasoned argument I could have offered.
It's interesting to note that the press is very selective about which griefs we pick out and build into a crusade. Almost everyone has heard of the Betts family, whose daughter Leah died because she did not know how to use ecstasy properly. Her family reacted by calling for even tougher prohibition. But how many readers have heard of Fulton Gillespie? After his son Scott died injecting adulterated heroin into his arm, Fulton began to rethink the "lock 'em up" approach he had always held towards drug users. Slowly, he came to believe that heroin legalisation is the only way to make drug users - and the rest of us - safer. So where's the "Legalise Heroin" campaign from the News of the World, waving Fulton into the nation's faces? Do they think anybody who supports drug prohibition is spitting on the corpse of Scott Gillespie? It seems that some griefs are more equal than others.
It is only the parents who call for harsh retribution and violent crackdowns that we hear about. We all know about the mother of James Bulger, who has tried to track down the two deeply disturbed children who murdered her toddler. But who knows about the Swedish parents whose child was murdered in very similar circumstances around the same time? They regard the child murderers as victims too, and they hold no vindictive grudge. No story there, then.
The best way to honour the dead - Sarah Payne, Leah Betts, Scott Gillespie, Casey Sheehan - is to make sure that fewer people join them in the grave. That requires us to stand back and take serious, rational decisions on the basis of evidence, not emotion. Sometimes those decisions will clash with the whims of their parents, who are locked in grief and pain and loss. It will seem cruel to tell them that sometimes a senseless death is simply a senseless death and nothing more, and that nothing good will come from their loss. But adopting policies that provide a false meaning and a fake coda, like Megan's law or the MMR madness, will end with even more dead kids. Creating more Sarah Paynes does the memory of Sarah Payne no favours.