In reporting the anti-war demonstrations today I've already heard a couple of news outlets, including ABC news, describe them as "possibly the largest anti-war demonstrations since Vietnam" as if that is supposed to give them some special weight and gravity. Other than some anti-nuke protests in the 80's and protests against the first Gulf War have there really been any significant anti-war demonstrations to speak of since Vietnam? Not that I can think of. But it sounds impressive and it you don't understand the background you could attach more meaning to it than it deserves.
The wording also contains the unstated implication that we all know that the war protesters ended the Vietnam War and so if anti-war demonstrations today are of the same scope and size they too could prevent or end a war. The problem is that anti-war demonstrations did not end the Vietnam War. Sustained heavy bombing of North Vietnam, in particular Hanoi, in 1972 brought the North Vietnamese to the table and ended the war. Watergate lost the war as Nixon was forced to resign and Ford was so weakened that he was unable to overcome Congress and honor the U.S. commitments to defend South Vietnam that had been a condition for the peace accords to succeed.
Part of the mythology of the 60's and early 70's was that the anti-war protests gradually convinced the majority of Americans that the war was wrong and that's why it ended. Not so. It that was true that how could one explain the 1972 presidential election when Nixon, the embodiment of the evil war monger according to the peace movement, absolutely crushed peace candidate George McGovern. 520 electoral votes for Nixon to 17 for McGovern. I guess not everyone was burning draft cards and putting flowers in gun barrels.