This is what we call 'confirmation bias'. Societies all over the world that have lasted millenia have had some form of bisexuality or homosexuality.
Once they collapse due to other factors after millenia of having a fairly benign non-heterosexual minority, historical revisionists with current political biases will try to claim that it was because of any sexual behaviour they do not approve of.
In reality, there is heavy evidence to suggest many antic societies (such as Greco-Roman antiquity)began to collapse at the same time that sexual behaviour was frowned upon.
It makes sense; if you get a population hating sex to the point that it becomes taboo, it is more likely to take that hatred out on factors unrelated to sexual behaviour; fellow neighbours, the government, etc etc.
The Orwellian notion that sexual furor is deliberately replaced by political and authoritative worship in repressive societies is a logical sequence of reasoning.
Just as flocks of birds will 'wipe' their beaks on perches as a form of self-masochism so as not to compromise collectivism, the human species practices similar enforced ideals of self harm to avoid the possibility of rebellion.