He's a very reputable theoretical quantum physicist with several respectable results to his name. I know because my PhD was in a similar field. You could perhaps accuse him of ignorance of results in other specialities, but not crankism.
Not necessarily. Linus Pauling had several respectable results to his name, too. Even the smartest people can be so wrong when working in fields even a little bit outside their specialism that they are almost indistinguishable from cranks.
This IS his field of research.
I only accused the author of doing a bad job of not looking like a crank. I realize that non-cranks do that sometimes.