Christian poetry, in Britain, has become nearly as invisible as God - partially due, no doubt, to the fear on the part of would-be practitioners of such verse, that such discourse would lead away from the irony, or ambiguity, expected (or required) of poetry now, towards something too dogmatic, earnest, or even, "too emotional".
I'm not exactly sure that Christian poetry is that invisble. Of course, it largely depends on what Swift means by "Christian poetry", which he doesn't define, and my reluctance to agree with his assessment might in large part be due to my being an enthusiast and practitioner.
However, I wouldn't call the career of Michael Symmons Roberts, for instance, invisble. Let's not forget that his collection Corpus, which is profoundly Christian in its concerns and imagery while also being fresh and contemporary in the same, won the Whitbread poetry prize in 2004. Nobody can understand Michael's work properly without understanding how it arises from and interacts with his Christian faith.
Perhaps it might not be so obvious that another Cape poet, Robert Crawford, is a Christian, but a reading of his work with this in mind will shed light on the impetus for, and imagery of, a number of his poems. Les Murray, of course, while not being a British poet, is still a well-known figure in these islands and, again, Christianity is a strong feature of his work. Then there's Gillian Allnutt, who might be best described as post-Christian but cannot be described as anything other than a religious poet.
I wouldn't call that invisble.
Swift also says:
Christian poetry... needs to engage with the difficult, the tentative aspects of its style, its subject area ... - appropriate, since language, too, is invested with the same problematic, indeterminate elements as faith. It is only the (empirically or theologically) strident that needs to be resisted, not writing which seeks, inquires, and, importantly, ethically engages, with the mystery - and yes, often the beauty - of existence.
Well, that seems to me to be a reasonable description of what the above-named writers are up to, in different ways and with different musics; it's also not a bad description of what I aim for.
Perhaps the invisiblity Swift feels is less to do with the degree to which faith shapes the poems contemporary Christian writers produce, the way it shapes them or how that shape is received in the wider poetry--which I have generally found to be warm--than with the growing blind spot in wider society's knowledge and understanding when it comes to Christian, or any other, faith. The challenge for religious poetry in this society is not only to do what Swift says above but to find ways of doing it that neither ignore the riches and depths of religious traditions nor lean on them in a lazy, uncommunicative fashion. That said, Swift's small contribution to bringing into wider view the possibilities of contemporary poetry with a Christian perspective is certainly most welcome.