Oh my god - you mustn't hold a degree to do scholarly work.
Mr Mehlberg collects songs considered bawdy - now what? Such songs sung by the people ARE folk songs, like them or not. In writing history as seen by the mighty they also make a good contrast what people really think.
There are only a few collectors of this sort of songs, and we should be glad to have them.
When I needed money as a student I worked sometimes on construction sites. There you could hear songs from the masons and carpenters your ears would fall of when you heard them. But a true philologus must be accustomed to all levels of speech, even if it is concerned with a lot of sexual intercourse and venereal diseases.