economists carried out bloodless coups of central banks
  around the globe, co-opting the essentially arbitrary 
  and political matter of setting interest rates 
  for themselves.

Interest rates not set by politicians? I think thats been a societal good - though I worry that the independence of the Fed could be undermined by the next president depending on how things go.

  [...] bolstered economics as a tool for governing
  technocratically and shutting down people who disagree 
  with the elite consensus

The dawn of a new conspiracy theory.

  Economics is not a science

Correct. Lets qualify that - it is a social science. This is a stated thing and not hidden. No one claims its a science on the level of physics or chemistry.

  economics also lacks the basic accountability mechanism that real sciences have

In that sense, yes - its a social science. It is not the same. I defer to others on how that is good/bad but the comparison is off.

I don't think the author knows what economics really is (which is shocking "Ben is in his second year of UChicago’s JD-MBA"), but hey, he made the front page on HN.