David Graeber is an anthropologist. He apparently did a PhD thesis on "magic, slavery, and politics." What qualifies him to talk about the economy and the function of various jobs? I mean, hell, he's an anthropology professor declaring other jobs to be "bullshit." (But I won't go so far as to say "anthropology professor" is a bullshit job, because I'm self aware enough to realize that I probably just don't understand what economic function they perform.)

Anthropologists are not qualified to decide whose job is bullshit and neither is anyone else. That's the whole premise of the book. Anthropologists however are trained to listen to what people say about their own lives and understandings of it and that's what I did - a bullshit job is defined as one which the person doing the job believes doesn't have to, or shouldn't, exist.