So Afghanistan is one of the poorest countries in the world, we've been fighting there for almost 8 years, and we actually have a significant number of "coalition" troops helping us, and yet apparently the Taliban has regrouped and is resurgent against our corrupt puppet government that's never had much influence beyond the capital city/state.
If anyone believes that our war there, such as it is, is still winnable, then they are effectively saying that although Dubya screwed everything else up royally, he somehow managed to effectively conduct our war in Afghanistan (while torturing in secret prisons and privatizing much of the military operation). Seems like long prima facie odds there.
Afghanistan is the original Vietnam analogy. Back in 1979 we intentionally lured the Soviet Union into invading, to "give them their Vietnam". We know that nobody in many centuries has ever managed to conquer Afghanistan. And yet now people think we have some winnable cause to be won through military occupation? And after being military occupiers there for over 7 years we think that there is some military solution still in the future? Ridiculous. And woefully immoral.