F.J.C. has a good many things to answer for:
1) If he hadn't decoded Chaucer, English majors would have escaped The Canterbury Tales. They would have been too hard.
2) His best-known student was George Kittredge. You're reading King Lear and you come to "My life has fallen in to the sere," and you say to yourself, "What the hell is a sere?" So you look it up in Kittredge's glossary: the space between the strike plate and the hammer of a pistol. Oh dear, that's an anachronism, I'll have to remember sere. In the hands of the right professor, Kittredge can destroy the poetry of even Shakespeare.
3) Unlike Cecil Sharp, Child seems to have paid little attention to the tunes of his ballads.
4) "Oral literature" makes no sense and it leads to the false idea that the oldest version of a ballad is the best, or that we should pick out a good version,rather than consider the collection of versions as one entity.
5) It was inconsiderate of him to die before writing up his criteria for selection. Bonny James Campbell is a beautiful song, and I'm glad he included it. But what's the story? James goes off to battle and gets killed. His wife, his mother, and perhaps his horse are sorry about this.