(this post started out as an introduction to my review of Camouflage... and then just kept growing, so I decided to make it its own post)
Joe Haldeman is best known for his novels Forever War and Forever Peace, neither of which I have read. From what I understand, however, Forever War was a scathing commentary on the Vietnam War, thereby doing what science fiction does best - thinly discussing a critique on a current problem that everybody else is perfectly comfortable critiquing without the disguise (that is, when it is critiquing an old issue that everyone is perfectly comfortable talking about out in the open).
I actually think that science fiction can be quite good at critiquing issues that people don't feel comfortable talking about. On the other hand it seems that, at least in modern science fiction, people do a lot of disguising of things that don't need to be disguised, just so they can pat themselves on the back for having commented on a political issue. I think now, for example, of Battlestar Galactica, which did a commentary on the Iraq War when everyone was already opposed, or District 9 which commented on apartheid (what shall we do next, make a science fiction story that is a disguised portrait of how evil the Nazis were?).
Ultimately, I don't think science fiction has to be a commentary on anything, it can tell good stories and weave important myths. But, if you're going to use it as a vehicle for veiled social commentary, at least comment on something worthy of being veiled.