'his preferences were weighted by his own elite background'. (SG referring to some of Child's attitudes to the ballads, many of which I happen to agree with) He was from a middle-class background. His friends were mostly poets and dignitaries of the Boston elite. He was Professor of English at Harvard. His previous work included a 30-vol critical edition of 'The English Poets'.Don't you think that colours some of his choices?
BTW I certainly wouldn't use the word 'elitist' to describe him in general. You can if you want. As I keep saying and will continue to say his work in our field has never been surpassed but that doesn't mean we have to worship him like a god and it doesn't mean he was beyond making errors.