It wasn't the Fabian Society. It was the general secretary of the Fabian Society in a personal capacity.
The Fabian Society never gives a view.
'Fabian Society analysis paper
Stuck
How Labour is too weak to win, and too strong to die
Author: Andrew Harrop, General Secretary, Fabian Society
Date: 3rd January 2017
Facing the Future is the Fabian Society’s programme on Labour’s renewal. It brings together a broad range of voices to challenge the Labour Party to do better for the people who need it most.
Through events, publications and research, we are ensuring that Labour has the fundamental debate that it needs on its purpose, organisation and ideas. Labour must make itself relevant for the 2020s and broaden its appeal to people who rejected it in 2015.
This paper, like all publications of the Fabian Society, represents not the collective views of the Society but only the views of the author.'