"By the way, James, there are a lot of traditional leftists who hate Derrida for promoting self-doubt among intellectuals. You rightly point to the decline of the radical labor movement as key to the crisis of Marxism, but do you think the intellectuals were/are wrong to become so self-questioning, and skeptical of, yadda yadda, master narratives?"
It is a good question, but first a proviso. Derrida was a philosopher, and deserves to have his philosophy looked at in its own right, independent of any political conclusions. There is no doubt that there is a lot of technical developments in it that are admirable in their own right, but I think it is ultimately flawed. The relationship between politics was opened up for discussion by Derrida insofar as he addressed Marx - but that would not exhaust his work, by any stretch.
So to answer your question, I would say that, insofar as you can see Derrida (and the wider 'deconstruction' school that followed him) as inaugurating a general deconstruction of master narratives, that is rather problematic. I mean that a critique that in its basic outlines is applicable to all ideologies, is one that treats their actual content as incidental, addressing only their form. It reduces liberalism to marxism to fascism. All are 'grand narratives'. To push the point one could say that it leaves them all untouched in their particulars. Deconstruction can sit happily alongside an ironic, self-knowing imperialism, such as we see argued by the EU official Robert Cooper.
So, no, of course it is not wrong to criticise received opinion. But a blanket criticism is no criticism at all. (Indeed, to paraphrase Alasdair MacIntyre, deconstruction of master narratives is itself a master narrative.) What deconstruction offered to students was a cheap erudition that allowed them to dismiss schools of thought without ever really bothering to master them.
The attraction for me of Marxism (and Hegelianism) is that it develops thought through criticism. But deconstruction only deconstructs. As Francis Bacon says somewhere the difference between me and the sceptics is that I doubt everything at the first setting out, as a way towards greater knowledge, but they see doubt as the goal (paraphrase from memory).
More than that, and this is unreasonably to make Derrida stand in for a general movement, the post-modern moment seemed like it was a radical position coming from the margins, but by the 1990s it was more like the mainstream, characteristic of a corrosive scepticism, that ran alongside a broad disengagement with politics. It was close to being the dominant ideology of the age (never wholly of course - there is no gainsaying the enduring traction that free markets, family and nation have on people).