Tarring all of postmodern theory with the Sokal hoax brush is like claiming that all of medicine is a fraud because of the Thalidomide disaster. Not saying you're necessarily wrong, just that your reasoning here is at least as lazy and flawed as you're implying post modern theory to be.
The hoax itself didn't undermine it all. You could reasonably make the case that it Social Text was simply lazy and just published shit w/o reading it.
Reading about the hoax, however, is a good way to introduce people to what PoMo theory is, and the problems with it, as it introduces some important people and perhaps the biggest criticism of lit-crit (that being the emperor has no clothes).
I read quite a bit of PoMo stuff in college, kept waiting for a point for it all to make sense. Ultimately, I realized it was just a giant community of fakes and charlatans with little of value to say.
The problem with arguing with lit-crit types is you cannot argue on their terms. Their game is a game of empty words, built upon the ramblings of countless self-indulgent writers and pseudo-philosophers before them.
There's nothing in the way of reality to anchor anything they say, so anything can be said, and points are scored for the most convoluted explanations of.... well... nothing. It's downright embarrassing.
But don't believe me, go read some for yourself and decide.
Oh, and Estragon, there was actually nothing in the way of 'reasoning' in my original comment. I simply gave a quick opinion and a single link that those interested in it might find interesting. I'm not sure why you construed it as such.
You're completely disregarding the fact that at least Derrida has made substantial and widely acknowledged contributions to his field. He's not in the same category as Lacan or 'the lit crit types'. Disregarding all of postmodernism based on the excesses it brought forth is as unwise as disregarding everything Nietzsche wrote based on him dying rather insane.