Apologies for the condescension, but honestly: when even the American public (more than two-thirds of whom support this research) achieves a consensus on an issue, it can't be too hard to resolve. So the more interesting question isn't who's in the right, but what is the curious minority myopia that has produced a debate at all?

Earlier this week, we saw much grandstanding from both queasy, refuse-to-get-their-hands-dirty countries such as Austria, which would flat-out ban the use of EU funds for this research, and others - not only Britain but, impressively, Catholic Portugal - which would forge ahead with EU financing. For once, the compromise agreement - to allow individual states to determine whether they will use EU science funds for stem-cell research - seems eminently sensible.

Alas, it's impossible to characterise as "sensible" Bush's putting the kibosh on a bill to provide federal funds for embryonic stem-cell research last week, conspicuously the first veto of his presidency. Making the announcement, Bush surrounded himself bathetically with babies, all the results of "adopted" embryos otherwise marked for disposal. Yet nothing about the pursuit of this research precludes individual couples continuing to bid for abandoned embryos from fertility treatments, the vast majority of which will still end up in the bin. Indeed, after an ill-judged White House assertion that Bush considers destroying human embryos as tantamount to "murder", stem-cell research supporters accurately observed that in that event fertility clinics should be prosecuted for homicide. Hauling clinics into court for discarding a few clumps of cells would be OTT even for the Bush administration, which subsequently back-pedalled in embarrassment.

Exercising his only veto to date in defence of biological material undetectable to the naked eye, this president went to war in Iraq with nary a thought for the consequences, pursuing a fool's errand that has cost tens of thousands of lives. Mind, we're talking about the lives of whole, big people, the kind that talk and walk around, with families and fast friends, with senses of humour and gifts for writing poetry. Not tiny clusters of cells, which will never trot into the room when you call should you scream yourself blue in the face.

On both the left and right, a certain sanctimonious social subsection chronically indulges the moral equivalent of penny-wise, pound-foolish. This over-scrupulous ethical bean-counting of the little stuff, and utter profligacy in relation to the large, contributes a shrill note in debates about a host of other matters: assisted suicide for the terminally ill; abortion; questions such as whether we should keep babies alive at any cost even if they're in agony and doomed to die; and cases such as Terri Schiavo's, which roiled the entire US for months over the fate of a woman who was, as an autopsy subsequently established, brain dead.

Yet these dainty moral purists are rarely anguished about going to war, or even about capital punishment. They're not likely to get worked up about an entire continent of big people who live on less than £1 a day. Typically, hyper-purists don't give a frig about the practical consequences of their fastidiousness. They aren't in the least concerned about dashing the hopes of diabetes patients, forcing the terminally ill to suffer one more hateful day, or making already overstressed healthcare systems finance their personal self-righteousness at the sacrifice of caring for people who can actually get better.

This variety of moral purism has nothing to do with concern for others. It is a vanity. It is not about principle, but about appearing principled. It's about look-at-me-I'm-so-virtuous - a preening, self-congratulatory contingent to which Bush was pandering last week. And, of course, it's also about bossing us other, less worthy moral scruff around.

Philip Roth's American Pastoral portrays an ostentatiously lofty girl named Merry - a mischievous appellation, since she sure ain't a lot of fun. Merry is so obsessed with doing no harm to a single living creature, no matter how microscopic, that she won't eat, won't wash, won't even walk on the ground. Novelistically, Merry is a brilliant creation, albeit functionally insane, and one of the most supremely irritating characters I have encountered in fiction. And she stinks. Metaphorically, the holier-than-thou crowd always does.

Monday's announcement that this year Transport for London is set to spend even more than 2005's £11.5m on advertising stirred an ongoing rage. Whenever I see those costly television adverts promoting cycling in the capital, with cheery, healthy young people in helmets bouncing off their mountain bikes and looking refreshed, I cannot stay seated from fury.

I object on the basis of false advertising. Realistically, those young people should be bouncing off the Tarmac. If mayor Livingstone must run promotions for cycling, he should be broadcasting images of cyclists being cut off at speed by left-turning vehicles that haven't signalled; sent sailing from opened car-doors; verbally abused by drivers who have just violated the cyclist's right-of-way (since there's none so indignant as the one in the wrong); quite reasonably cautioned or ticketed for running a light, but by police who never, ever ticket drivers who plough pedallers off the road unless the cyclist ends up dead; and veering around cars parked - often legally - in the rare bike lane that goes anywhere, only to be flattened by a truck.

That, friends, is cycling in London. So if Transport for London is intent on squandering its scarce resources on adverts, instead of using them to make cycling safe, it might replace its slogan "Get on your bike!" with "Write a will."

· Catherine Bennett returns next week

· This week Lionel read TC Boyle's Talk Talk: "After Drop City, I'm on the Boyle boil! Riveting novel about it-could-be-you ID theft. I'm a joyfully grovelling, sycophantic fan." Lionel watched back-to-back news reports on Hizbullah "since with hundreds of cable channels in the US, naturally there's nothing on."