What's with Postmodernism?

When I write, I usually pick topics that I understand. Well, there's one topic in skepticism that I feel I don't quite get. What's up with skepticism's relationship with postmodernism? If you pay attention to the conversation that's going on (and I've heard this both offline and online), you find that most skeptics think postmodernism is one of their enemies. Why?

First, a few links to demonstrate what I'm talking about (and yes, I do bookmark these for months at a time).

• The Sokal affair - Alan Sokal famously published a nonsense article ("Transgressing Boundaries: Towards a Transformative Hermeneutics of Quantum Gravity") in a postmodern journal without the editors catching it. This experiment suggests that postmodernism is indistinguishable from nonsense.
  
• Rob Knop runs into a postmodernist who promptly dismisses Big Bang theory as being a cultural projection.
• A postmodernist critique of evolution - The association between postmodernism and Creationism speaks very badly of postmodernism.
  
• A retrospective look at postmodernism - Rob Helpychalk gives us a more historical perspective on postmodernism. He gives a pretty good answer to my question "What's with Postmodernism?" but I guess I'm still confused.
  

What is postmodernism? It's so hard to define, especially by me, since I'm young and have absolutely no historical perspective, and do not study humanities. Everything I say on this topic is without the slightest bit of authority. But basically, postmodernism is a set of ideas that has cut across all fields of study, and has greatly affected our culture. Sometimes, it's defined as the rejection of all meta-narratives (meaning that they do not accept that there is any "correct" overarching worldview). Every view is ultimately affected by the cultural context, and in the more extreme forms of postmodernism, every view is purely a construction of its cultural context. In the even more extreme forms, scientific facts are no exception. You can make reality into whatever you want it to be.

When skeptics think of postmodernism, they mostly seem to think about the more extreme forms that reject science. Well, we're used to focusing on the bad parts of everything, because that's where criticism helps most. But to condemn all of postmodernism based only on the extreme forms is to construct a strawman. I mean, the idea that there is no reality separate from our worldview is silly, but the less extreme forms aren't all bad. It's true that there is some degree of bias from our culture, and we have to keep the uncertainty of our own beliefs in mind.

From virtually every other source, I get a very different view of postmodernism. We live in the Postmodern era, which started maybe around WWII. So really, we're all postmodernists. Here's my extremely apocryphal impression of modernism and postmodernism:

Modernism: "Look back at all of history. Those guys don't know what they're talking about! We can do much better than that! Instead of looking at the past, we should be looking to the future. In the future, there will be no war, and we'll have flying cars!"

Postmodernism: "Look back at all of history. Those guys don't know what they're talking about! And based on the historical results, we find that modernism didn't know what it was talking about either. We're no different. Everything we've ever known has been molded by our culture. How can we know what is true anymore? How can anyone know?"

If postmodernism is a cultural era, then it follows that even the skeptical movement itself is a postmodern movement. After all, the skeptical movement is usually traced back to, what, the 70s? I could draw similarities--skepticism rejects all sorts of meta-narratives, and is forever mindful of uncertainties. But one of those meta-narratives they reject is postmodernism, so maybe skepticism is really a modernist backlash against postmodernism? Or maybe it's something else entirely?

So I'm confused. It's up to you, the internet, to set me straight!