I have no hostility to religion as such, and I think that there is much to learn from the way Latour extracts religion out of the mode of REF and of belief. However, I don’t think that a separate mode REL is the best way to do justice to religion historically, sociologically, and anthropologically. Also, I disapprove of smuggling credal assumptions into a text that is not supposed to be a theological treatise, but an “empirical” ontology. A philosophical text that is far more widely welcomed by priests and theologians than by philosophers raises doubts and questions.
I don’t think that the reserves expressed on Latour’s treatment of religion are due to dusty abstract philosophers being unable to cope with empirical investigation, but rather they are due to people finding that the inquiry is not empirical enough.
For those who are Christians the reduction of religion to the mode REL has devastating consequences. Not only does God does not exist in a referential sense, but neither does Jesus (or if it could be shown that he did exist, it would be irrelevant). The Gospels, on this analysis, describe no empirical historical facts, as they are not referential texts but propose the “wisdom” or the “poetry” of REL. So with Jesus non-existent or irrelevant we have REL as a Christ-without-Jesus mode, that very few Christians would recognise as the essence of their faith.
REL as mode is doing no service to Christianity, unless you are whole-heartedly embracing the refined, or symbolic, Christ-without-Jesus version.