In post-structuralism, it is seen as one of several influential characteristics or tendencies of Western and Western-derived thought, and that typically, one of the two opposites assumes a role of dominance over the other. The categorization of binary oppositions is "often value-laden and ethnocentric", with an illusory order and superficial meaning.
A classic example of a binary opposition is the presence-absence dichotomy. In much of Western thought, including structuralism, distinguishing between presence and absence, viewed as polar opposites, is a fundamental element of thought in many cultures. In addition, according to post-structuralist criticisms, presence occupies a position of dominance in Western thought over absence, because absence is traditionally seen as what you get when you take away presence. (Had absence been dominant, presence might have most naturally been seen as what you get when you take away an absence.)
A more concrete example of a binary opposition is the male-female dichotomy. Some western thinkers, including structuralists, believe that the world is organized according to male and female constructs, roles, words, and ideas. A post-structuralist view is that male can be seen, according to traditional Western thought, as dominant over female because male is the presence of a phallus, while the vagina is an absence or loss. (Alternatively, Western thought could have viewed female as a presence, and male, subordinately, as the absence, or loss, of an invagination or theoretical "hole" of some kind.) The correspondence between each of the dominant Western concepts such as presence and male, as well as others such as rational (vs. emotional), mind (vs. body), thoughts and speech (vs. writings) are thought to show a tendency of Western thought called logocentrism or phallogocentrism.
The critique of binary oppositions is an important part of post-feminism, post-colonialism, post-anarchism, and critical race theory, which argue that the perceived binary dichotomy between man/woman, civilized/savage, and caucasian/non-caucasian have perpetuated and legitimized Western power structures favoring "civilized" white men.
Post-structural criticism of binary oppositions is not simply the reversal of the opposition, but its deconstruction, which is described as apolitical—that is, not intrinsically favoring one arm of a binary opposition over the other. Deconstruction is the "event" or "moment" at which a binary opposition is thought to contradict itself, and undermine its own authority. Although deconstruction can not explain how a rational basis for defending itself can then be maintained after it has removed any objective basis in structuralism it may have had.