Agreed. The worst casualties since the First(Spoiler Alert!
)Civil War.
Joking aside, think about that for a moment: more American soldiers died in Vietnam than in the European and Pacific Theatres during WWII. And all for nothing. Vietnam fell and the world shrugged and moved on. It wasn't the First Domino. It didn't cause every other country in South East Asia to turn Communist. It was never an existential threat to the US in the way the Nazis and Japanese were. It was brutal, sordid little war, fought for the most part by boys from poor neighbourhoods who had no chance of avoiding the Draft. And the ones who survived returned home and found themselves regarded as an embarrassment at best, war criminals at worst.
Ali had every right to tell the US Army to go take a flying fuck at a rolling doughnut.