We probably COULD have won the Vietnam War militarily. But to "win" there would have meant forcing the South Vietnamese to accept a government (Catholic in a Bhuddist-majority country, full of ties to the hated, and expelled, French colonial powers) that they loathed. And that would have to be accomplished with massive brute force and have involved staying in the country for years on end.

In short, it would have required us to act just like the regimes we hated. Like the Viet Cong, Soviet toadies who masqueraded as nationalists to win over the Vietnamese population (the one positive effect of our long stay in the country is that it exhausted the VC to the point that they gave up their plans to spread Communism all over Southeast Asia--in the end, they were willing to collect the other half of the country and call it a day). The growing skepticism about the Vietnam misadventure wasn't defeatism--it was a sign that the American people still had a functioning conscience . . .