It's not so black and white as that, Naveed. Yes,
  cross-disciplinary opinion is fascinating and makes for great
  book. I'm not knocking them. Dawkins had fascinating things to
  say about lot of thing that weren't evolutionary biology.
  *
  Yet, I would trust him on his branch of evolutionary biology to
  be an expert in his branch of evolutionary biology.
  *
  Everything else he writes about, I would take as the opinion of
  an evolutionary biologist speaking of his opinion from within
  that branch of evolutionary biology about subjects that are not
  evolutionary biology but how they are "as seen by his unique
  lens" and also as a person like you or me.
  *
  He can cast a unique light on subjects that he's not an expert
  in by the glasses he's wearing from HIS perspective FROM his
  field.
  *
  They are interesting. They're worth listening to. At the same
  time, can you see the distinction I'm making?