I happen to disagree with his conclusions, based on the writings of a number of mystics who outline the birth of Christ in greater detail. (eg. Maria Valtorta) The place where Jesus was born was in fact a place where animals were kept, but it is decribed by her as a "cave." There were animals present, they helped provide warmth on what was a VERY cold night.

Whether the traditional view of animals plus singing angels is true or not, it is certainly harmless to view it this way. What could be his motive for ruining the traditional image? Seems to give more firepower to people who want to call religious belief "a bunch of made up stories."

Angels would have every reason to sing at the birth of Christ, and they did so in the presence of the shepherds. (interestingly, the shepherds were ostracized by many people for what they had witnessed)