There are, I think, some heuristic problems with doing it too broadly, but, when they happen, comparisons between Iraq and Vietnam usually come from war opponents, not war advocates. I find it really odd, then, that Eric Edelman, the undersecretary for policy at the Defense Department in the course of attacking Hillary Clinton, said this: "Premature and public discussion of the withdrawal of U.S. forces from Iraq reinforces enemy propaganda that the United States will abandon its allies in Iraq, much as we are perceived to have done in Vietnam, Lebanon and Somalia."
We can even leave Lebanon and Somalia out. It's really abundantly clear that there are hawks out there who really think things would have been a lot better if, say, six million Vietnamese had died, if we had a few thousand troops in South Vietnam, and North Vietnam looked a lot like North Korea. At least then we wouldn't be castigated for having abandoned our allies by the zero people out there castigating us for that.