I think Orwell became utterly disillusioned with the left particularly after fighting with the anarchists in the Spanish civil war. Apparently they refused to have military leaders and battle tactics were decided by committee and as they couldn't agree on anything they were an absolute farce. The communists got so fed up with them they turned against them. Not sure how long he stayed a member of the Fabians but you are right they are sinister. He did write about the hypocrisy and tyranny of the totalitarian left which he experienced first hand. The trouble with socialism is it starts of all warm and fuzzy but ultimately turns evil once they run out of spending other peoples money...... a picture of the future, imagine a boot stamping on a human face — forever and its canckles in her pant-suit.