> The lack of privacy, the moralizing.. combined with a too-far removed central authority?
Remember that Orwell was writing quite close parodies of Stalinism, based on his encounters with actual Stalinists while fighting for the socialist side in the Spanish civil war. In Animal Farm, Snowball is Trotsky, and so on. So he undoubtedly had something specific in mind when inventing the "anti-sex league", although I'm not quite sure what. But lack of privacy, moralizing, and remote unaccountable central authority? He means Stalinism.
Remember also that it's a front, in which Julia participates cynically for her own safety: ( https://orwell.ru/library/novels/1984/english/en_p_2 )
> " ‘Actually I am that sort of girl, to look at. I'm good at games. I was a troop-leader in the Spies. I do voluntary work three evenings a week for the Junior Anti-Sex League. Hours and hours I've spent pasting their bloody rot all over London. I always carry one end of a banner in the processions. I always look cheerful and I never shirk anything. Always yell with the crowd, that's what I say. It's the only way to be safe.’"
> In the old days, he thought, a man looked at a girl's body and saw that it was desirable, and that was the end of the story. But you could not have pure love or pure lust nowadays. No emotion was pure, because everything was mixed up with fear and hatred. Their embrace had been a battle, the climax a victory. It was a blow struck against the Party. It was a political act.
And later on Orwell tells us directly what the Anti-Sex league was intended to achieve:
> She began to enlarge upon the subject. With Julia, everything came back to her own sexuality. As soon as this was touched upon in any way she was capable of great acuteness. Unlike Winston, she had grasped the inner meaning of the Party's sexual puritanism. It was not merely that the sex instinct created a world of its own which was outside the Party's control and which therefore had to be destroyed if possible. What was more important was that sexual privation induced hysteria, which was desirable because it could be transformed into war-fever and leader-worship. The way she put it was:
> ‘When you make love you're using up energy; and afterwards you feel happy and don't give a damn for anything. They can't bear you to feel like that. They want you to be bursting with energy all the time. All this marching up and down and cheering and waving flags is simply sex gone sour. If you're happy inside yourself, why should you get excited about Big Brother and the Three-Year Plans and the Two Minutes Hate and all the rest of their bloody rot?’
> That was very true, he thought. There was a direct intimate connexion between chastity and political orthodoxy. For how could the fear, the hatred, and the lunatic credulity which the Party needed in its members be kept at the right pitch, except by bottling down some powerful instinct and using it as a driving force? The sex impulse was dangerous to the Party, and the Party had turned it to account. They had played a similar trick with the instinct of parenthood. The family could not actually be abolished, and, indeed, people were encouraged to be fond of their children, in almost the old-fashioned way. The children, on the other hand, were systematically turned against their parents and taught to spy on them and report their deviations. The family had become in effect an extension of the Thought Police. It was a device by means of which everyone could be surrounded night and day by informers who knew him intimately.
(The red sash business reminds me of the "silver ring thing"; US evangelist Christians replicating similar systems of control and moralizing among their young people)