The reality was that neither Johnson nor Nixon had any idea of how to win the war and just let it go on chewing up people because they couldn't figure out how to quit without losing face.
Kerry may not have been 'patriotic', but neither were the pro-war politicians he was criticizing; they just used patriotism.
/2/ Kerry helped influence Congress to cut off all military resupply to the RVN. Without bullets or fuel, the RVN was unable to defend itself, and the NVA rolled into Saigon in a conventional armored thrust.
You can thank Kerry and his commie loving pals for millions imprisoned in "reeduation camps" and dead in the killing fields. Yes, he helped to drive the US out of SE Asia. And he must take a large chunk of responsiblity for the horrors that followed.