Being neither British and automatically protective of the author, nor American and personally offended by some of the commentary, I'm maybe as close to impartial as is possible.
My takeaway was that the food wasn't especially good and the service was even worse. It wasn't really made clear how the room full of American golfers really impacted the author's night, so the pillorying of them came across as gratuitous.
"They were buoyant and they were ordering steaks" seems to be the extent of their crimes.
I will say, the British press elevates the restaurant reviewer far higher than I think is the case in American or Australian newspapers and as a result, Jay Rayner and Giles Coren as decent examples, they often tend to come across as reasonably full of themselves.