I think Devils Advocate is saying that it is more important to sing the songs, and to judeg the song on its merit as regards choice of singning it than to be concerned wheter it is tradtional or a composotion,his /her argument that we do not judge modern composed songs by who wrote them,is a valid argument, it is not silly.
Devils advocate, did not actually say that there should be no study of the history of songs, if i understood him /her correctly, Devil was saying that singers choose songs on their merit.
Devil does seem to imply that he?she thinks the most important worth is in singning them, that does not mean that devil thinks there is no worth in studying the history of songs.