A week ago it was the turn of the US philosopher Daniel Dennett, second only to Dawkins in the global ranking of contemporary Darwinians, to be similarly feted at a series of lectures and debates across the UK launching his book on religion, Breaking the Spell. The two make quite a team, each lavishing the other with generous praise as the philosopher Dennett brings to bear his discipline on the scientific findings of Dawkins.

The curious thing is that among those celebrating the prominence of these two Darwinians on both sides of the Atlantic is an unexpected constituency - the American creationist/intelligent-design lobby. Huh? Dawkins, in particular, has become their top pin-up.

How so? William Dembski (one of the leading lights of the US intelligent-design lobby) put it like this in an email to Dawkins: "I know that you personally don't believe in God, but I want to thank you for being such a wonderful foil for theism and for intelligent design more generally. In fact, I regularly tell my colleagues that you and your work are one of God's greatest gifts to the intelligent-design movement. So please, keep at it!"

But while Dembski, Dawkins and Dennett are sipping the champagne for their very different reasons, there is a party pooper. Michael Ruse, a prominent Darwinian philosopher (and an agnostic) based in the US, with a string of books on the subject, is exasperated: "Dawkins and Dennett are really dangerous, both at a moral and a legal level." The nub of Ruse's argument is that Darwinism does not lead ineluctably to atheism, and to claim that it does (as Dawkins does) provides the intelligent-design lobby with a legal loophole: "If Darwinism equals atheism then it can't be taught in US schools because of the constitutional separation of church and state. It gives the creationists a legal case. Dawkins and Dennett are handing these people a major tool."

There's no room for complacency, urged Ruse over lunch in London last week. Last December's court ruling against the teaching of intelligent design in some Pennsylvania schools may have been a blow, but now the strategy of the creationist/intelligent-design lobby is to "chisel away at school-board level" across the US. The National Centre for Science Education believes that as many as 20% of US schools are teaching creationism in some form. Evolution is losing the battle, says Ruse, and it's the fault of Dawkins and Dennett with their aggressive atheism: they are the creationists' best recruiting sergeants.

Ruse has got to a reckless stage of his career. He prefaced the essay he submitted for Dawkins's festschrift with the above quote from Dembski and went on to declare that he "felt intensely irritated with Dawkins ... It's bad enough having to fight the enemy without having to watch my back because of my friends." The editors were horrified and ordered a more deferential rewrite - which Ruse duly provided.

Even more reckless, Ruse put on the net an email exchange between himself and Dennett in which he accused his adversary of being an "absolute disaster" and of refusing to study Christianity seriously: "It is just plain silly and grotesquely immoral to claim that Christianity is simply a force for evil." Dennett's reply was an opaque one line: "I doubt you mean all the things you say."

But Ruse has got a point. Across the US, the battle over evolution in science teaching goes on. Just in the past month there have been bills in state legislatures in New York, Mississippi, Nevada and Arkansas promoting intelligent design. Last November the Kansas education board promulgated a new definition of science that allowed for supernatural explanations of natural phenomena. A school district in Kansas rebelled last month, accusing their board of "an utterly false belief that evolutionary science and the scientific method is based on atheistic philosophy. Promoting this false conflict between science and faith erects unnecessary barriers." At the heart of many of these local controversies is the firmly held belief that Darwinism leads to atheism, indeed that it is atheism. Across the US, a crude and erroneous conflict is being created between science as atheism and religion.

It's important that Britain avoids the trap that America is falling into, not just because it endangers good science, but also because there is a fascinating debate worth having about what scientific method can reveal about faith, and what theologians have to say about science. A raft of disciplines, from evolutionary biology and psychology to anthropology, are generating new insights into this persistent human phenomenon, religious belief. In the best parts of his book Dennett draws on these, as does the scientist Lewis Wolpert in his new book, Six Impossible Things Before Breakfast. Wolpert argues that the origins of religious belief are linked to our unique capacity to make tools; Dennett links it to a survival instinct to attribute agency to phenomena.

Both Dennett and Wolpert acknowledge that religion may have provided evolutionary advantages for humans. There's good evidence for faith improving mental health and optimism, and reducing stress; shamanism, with its placebo effect, was the best healthcare system for thousands of years. Dennett cites those who argue that faith improves cooperation within groups (though not between them). This argument raises the crucial question of whether, in an era of globalisation and limited resources, religion has outrun its evolutionary advantage.

This is the kind of conversation we want to have in this country, but we're not safe from American-style false dichotomies between faith and science yet (which would have particularly sharp consequences for the thousands of young Muslims in this country studying science). On the very day that Rowan Williams, the Archbishop of Canterbury, made a useful and unequivocal intervention rejecting creationism, Charles Clarke, at a conference on faith and the state, was wobbling precariously on the proverbial pinhead: "in schools it's a good debate to have". Little did he realise that he was using a line straight out of the creationists' lobbying manual: "teach the controversy".

Let's be clear, Clarke is wrong - some debates are not worth having. No one argues that it's a useful project for year 10s to research flat-earth theories, so why intelligent design? But if we agree on that, then equally we can also agree that some debates are so corrupted by prejudice and ignorance that they are also not worth having.

All protagonists in a debate have a moral responsibility to ensure that the hot air they are expending generates light, not just heat. It's a point that escapes Dawkins. His book on religion, The God Delusion, is to be published this autumn. Dembski and the intelligent-design lobby must already be on their knees, thanking God.

m.bunting@theguardian.com