North Vietnamese more reliable than Swiftees?

Why did Ted Koppel send reporters to North Vietnam to find out what happened in one of John Kerry's medal winning encounters with the enemy some 30 years ago? Why didn't Nightline rely on what Kerry's official biography says about the episode? Why didn't ABC rely on the account of the Swift Vets account of the battle? Because both Kerry's own bio and the recollections of the Swiftees differ with the official after action reports that Kerry wrote. Only Kerry's own account of the episode seems worthy of official military recognition, while all other accounts seem to suggest that Kerry did next to nothing other than to shoot a lone child in the back. Oh yea, I almost forgot. The North Vietnamese people under the watchful eye of government officials agree that Kerry was a hero.