I saw part 3 yesterday, where they showed an admin memo about the 10s of 1000s of troops added in late 1965 when S Vietnam was perhaps months from collapse. They actually assigned values to the reasons - 10% was to help the Vietnamese. You'd love to think that most of the remaining 90% was at least to fight communism and the domino effect, even if we now know that was all misguided - few thought it was then. Nope. 70% was to avoid embarrassment. Right there in black and white at the top of the page (70% overall - that's almost 80% of the remaining 90% after the stated portion actually helping the Vietnamese).

So, politicians of all stripes, here's a good general rule to follow - never, ever make momentous decisions simply to avoid embarrassment. Just selfishly for your own sake - it winds up being more embarrassing.