Postmodernism has sought to deconstruct every social institution, every meta-narrative (every narrative for that matter), every power structure basically because they believe they oppress people.
Yet Postmodernists deny the existence of any moral absolutes whatsoever.
So how can it be "wrong" to oppress people in a Postmodernist view?
(I ask as a concession to my limitations that if you are a Postmodernist that you attempt a clarity of language that will, I know, be difficult for you. Attempt to avoid dense, jargon-laden and obscure, "demanding interpretation" on my part. Skip the fragmented, impressionistic and void of logical connections designed to be "democratically inclusive discourse" forcing me to interpret what is being said and to take an active role in the creation of meaning. Conner, Postmodernistic Culture, p. 210.)