As you point out Kerry was no different than Bush, morally. He didn't choose combat in the way Jimmy Stewart or Clark Gable or Bush the elder did during WWII.
My first vote, and my third one, were for Nixon. I did indeed live through that era. I recall quite clearly that Vietnam was a topic of discussion during the Kennedy years but not a consuming one, because the number of military personnel in Viet Nam was orders of magnitude less than what it became under Johnson after Tonkin Gulf.But I do remember that the Diem government wasn't good enough for the reporters of the day, which is why Diem was dispatched. It was infuriating to hear the claims of his widow, Madam Nhu, that the US overthrew and murdered him. Unfortunately, it was true. That was a month before JFK was shot.
To me as a conservative, the post-Tet media opposition to Viet Nam came pretty much out of the blue; as a liberal you may have been better tuned to ealier vibes along that line.