Kerry had a phony war record as the SBVFT ably documented and Kerry never refuted. It was a legitimate issue in the campaign.
FYI: I am also a Vietnam veteran who served a full year in-country and eight months off the coast. Unlike Murtha, I totally support our invasion of Iraq and our continued presence there until the Mission is completed. That is the real lesson of Vietnam.
The lesson of Vietnam is that Vietnam fell because a Democratic Congress ended miliatry support of the South Vietnamese government and refused to let Ford hammer the North Vietnamese tank columns that were lumbering down the highways. The Democrats had bought the Kerry story that the American military was an instrument of the devil. They still believe that. Corollary to that was the belief in the goodness of the enemy. Nixon contributed to this by opening relations with Mao. In a way that was as cynical as Hitler's pact with Stalin.