identity politics as we understand them come from a french writer named foucault, who wrote widely about "hegemony" from this kind of depraved position. there's no deficit of criticism of foucault's writings from the left, most notably by habermas and chomsky, who both saw him as morally depraved. near the end of his life, he ended up supporting the iranian revolution, on the grounds that it would introduce a concept of moral purity in a collapse of capitalism; and, in this bizarre embrace of the most violent tendencies of fundamentalist islam, you can see his interest in what he called "hegemony" - the source of what we call "identity politics" was obsessed with the brutal application of hierarchy and power. one wonders if he might have tortured cats, as a child.
we don't have to wonder where this came from, though, as it's easy enough to trace.
the france of foucault's time was still a function of the revolution, so a substantial amount of his writing was created within it's context. any student of the french revolution is introduced to edmund burke, by necessity. speaking personally, i would have little interest in burke otherwise, but have read quite a bit of it due to his position in a lengthy series of arguments. you can't avoid him if you want to..
burke is otherwise known in england as the "father of modern conservatism" for creating a system where everybody knows his and her place, in an elaborate hierarchy with the church at the top and the peasants at the bottom. in burke's system, people are wholly defined by characteristics such as age, race, gender, place of birth and, of course, class. burke also wrote in favour of the american revolution (even while opposing the french one), but that is not important, right now.
what foucault actually did is take burke's system and flip it over on itself, before eventually subsuming his own politics within it. his entire concept of hegemony is fundamentally burkean in concept, to the point of being a logical conclusion.
now, people will argue that he was dismantling it, but that doesn't actually hold up - not any more than the arguments in favour of identity politics hold up today. he completely accepted burke's world view, then tried to find ways to subvert it - but always disingenuously, because he had that morbid attraction to authoritarianism, to hierarchy, to the enforcement of naked power with a blunt object.
the left has always seen through this, but liberalism picked it up at some point, and now we have this monster we have to slay before it gets out of hand. the iranian revolution may be an extreme analogy, but it is nonetheless where this goes if left completely unchecked.