Criticisms Of Postmodernism

1. Postmodernism undercuts the entire enterprise of education and truth.
2. To the extend that postmodernism indicts truth and value, postmodernism undercuts itself and whatever purposes and values it attempts to secure (i.e. less oppression, less violence, etc..)
3. Postmodernism is a poor analytic tool.  Whatever one gains with post-modernism, you take away from modernity.  For instance, turning all governments including democracies into equal parts tyranny doesn't exactly help fight for freedom or less oppression.  In addition, the norm to respect human dignity is different than the norm to take off your coat if you are going in doors--there are fundamentally different.  While I think geneaology might be able to handle this difference--the other tools fight against this.
4. Postmodernism undercuts rights protections (ie it would roll back the clock on the 60s reforms).  Progressive reforms & anything involving government protection of individual and groups would likewise die.
5. Postmodern focus on language trades-off with real world focus on actual oppression (not just the violence of language, but real violence).  You can spend too much time on issues of language or the essentialism of labels and forget to make the world a better place.
6. Postmodernism is too idealistic.  We as humans need structure (ie laws and guiding mission statements).  The idea that magically getting rid of those structures would be beneficial to everyone isn't true.
7. Postmodernism is grounded on hyperbole and overgeneralization--which is what it critiques modernism for.  It can ultimately become the fundamentalism it tries to critique.
8. Post-modernism results in hyper-individualism, without much in common.  The problems with this are described in Bowling Alone.
9. Most of postmoderns advantages can be captured by modern values and modern analytic tools.  You can examine power, ideology, and history without turning truth claims into mush.
10. Postmodernism results in ultimate relativism.  I've pointed to the problems of ethical relativism and relativism more broadly a number of times.  Here is one of those articles: A critique of relativistic theories of ethics
11. Assumptions & Caveats: To be fair, post-modernism is a rather broad field.  You would have to attack those folks around Heidegger, Nietzsche, Baudrillard, those postmoderns who talk about the nature of language, as well as a field-by-field analysis of the use of specific post-modern theories.