Having been to school with Dougie, and known him for over 40 years, - and also spent most of the last 12 days with him at his "Perthshire Amber" festival, I'm 99% certain that he did not intend any Christian / religious connotations whatsoever to be attached to that particular song. There is no evidence for that whatsoever that I'm aware of, and I've heard him introduce and sing it many, many times.
What other people make of it is of course up to them.