To postmodernists, we create our own truth. Every culture has its precepts and ways of looking at things. Postmodernists assume that the majority of people are conditioned by the dominant western paradigm or way of looking at things - which has served some groups well at the expense of others. In particular, white heterosexual males have profited at the expense of women, homosexuals, blacks, the disabled and other disadvantaged and minority groups. Postmodernists often challenge views of the world which they consider as sexist, racist, imperialist, fundamentalist or exploitative for whatever reasons, seeking to show the equal validity of minority perceptions and cultures.
Postmodernist thinkers see all 'concepts' as a product of society.
To them, we invent concepts and coin words to further our own political agendas - i.e. to get others to accept and ultimately bow to what we want. These concepts and values are therefore merely 'constructions' of certain self-interested groupings within society. The time has come for others to cast off their cultural shackles and make their presence felt in the marketplace of ideas. Postmodernists believe that we create our own truth, and that society creates us. This is seen as a very bad thing.