When I say 'religion and the decline of magic' I am not trying to suggest that this is an overtly (obviously) religious poem, although it does contain religious references, rather that it touches upon Pagan-esque view of the world that deals in the ancient rituals and practices that existed before mainstream religions. The speaker in the poem describes him or herself as someone who could help with horses, what has become known as a 'horse whisperer' because of their remarkable ability to manage difficult horses where more traditional approaches have failed. The act of horse whispering gains additional mystique through the horse whisperer's ability to work with horses in unconventional ways which is why the speaker refers to public anxiety that his/her abilities are the work of witchcraft. The early Pagan beliefs and mythologies held by people all over the world served to connect them to the natural world in ways that are hard for us to fully understand from the point of view of our modern lives. The shift from Pagan beliefs to mainstream religious doctrine has severed many of these links, and those who were accused of practicing these beliefs were branded as a dangerous witches and miscreants. What is important here is that in the context of the poem these references to witchcraft and ritual reconnect the reader to an alien world where we are intimately connected the world around us, so much so that people could talk (or whisper) to the animals.
One way of using this reading to unpack to the poem is to consider the act of horse whispering as an act of resistance or opposition to the