And continuing the theme of 'who benefits?', and because I'm not done ranting yet, I'm going to go off on a tangent here to give a concrete example of how postmodernism is used against oppressed groups - skip if you like! It concerns discourse in the history and archaeology of colonial Australia, which I encountered during my thesis.
Postmodern perspectives dominated Australian historical archaeology at that time, contending that it was simplistic and unfair to Aboriginal people to describe them as victims of European oppression. Instead, the trend was to identify acts of 'resistance' in the historical/archaeological record, to record a 'multitude of narratives', and instead of describing an oppressor–oppressed relationship, to conceive of black–white relations as a dialogue, a meeting of cultures, in which Aboriginal people transformed an oppressive situation by interacting with it and resisting in a multitude of ways, etc.
Now, there is nothing wrong with identifying acts of resistance to colonialism. But the whole narrative this produced, the effect of it, was to obscure what Europeans actually did. They were oppressors. It is no slight on Aboriginal people to describe them as victims of a brutal and genocidal regime. It is what actually happened. And here postmodernism blends with neoliberalism's victim-hatred. It's not shameful to be a victim, and nor does it mean you can't be an active subject - all it means is that you've been harmed by someone else. It's very telling that postmodernists, on the whole, hate 'victim' narratives (ostensibly because they denigrate women, PoC, etc, and 'deny them agency'). Who does this denial of victimhood really protect? As Kasja Ekis Ekman points out, if there are no victims, there can be no perpetrators.
And the knowledge this postmodernist discourse was producing was, in effect, obscuring the racism and brutality of Australia's past. The most prominent book on the area I was studying (the western NSW pastoral frontier) was called 'Shared Landscapes' - it described 'the multitude of voices' from Aboriginal people and pastoralists, their memories and attachments to the land. I found this disquieting at the time and now I find it positively cynical (especially since the study the book was based on was funded by the NSW government). It depicted all stories and histories as equally worthy of consideration, all ties to the land as equally valuable. There was no vertical power relationship here: just various conflicts (and, sometimes, friendships) between two groups of people who had been sharing the landscape for a long time. The NSW pastoral frontier was one of the bloodiest places on earth in the early to mid 19th century, and the violence was overwhelmingly one-sided: it involved mass killings of Aborigines and seizure of their land by both the military and civilians; incredible brutality, both casual and strategic, on the part of the pastoralists (I read their diaries) YET, the narrative that white Australian postmodernist historians produced talked of 'shared landscapes' and denigrated (to use Butlerian phrasing) 'simple and paralysing models of structural oppression' - all the while pretending to take an anti-racist and pro-Indigenous view by by 'foregrounding alternative narratives'. Again I ask, who does this serve?
Can't resist quoting from that book, because it eerily echoes the obscurantist BS that Butler disseminates about gender:
In shifting the reader’s gaze to begin to see pastoral history as shared between black and white Australians, the pastoral frontier becomes a ‘contact zone’. Mary-Louise Pratt uses this term (1992: 6) ? in opposition to ‘frontier’, which historically has been grounded within a Euro-American imperial expansionist perspective...
Right, see: we have to euphemistically rename a violent expanding imperialist frontier as a 'contact zone' - lest we risk reproducing the 'Euro-American imperial expansionist perspective' by, um, naming the real-world consequences of that perspective.
In the same way, as OutsSelf noted, Butler contends that the discursive category of 'woman' produces women's oppression. A neat trick that turns feminists into the reproducers of women's oppression, because there is no way to do feminist analysis without referring to women as a discursive category.