These were the internal affairs of Vietnam! And no one is allowed to intervene and solve for the Vietnamese people like him live!
The Vietnam War, like all wars, was not an internal affair. When one group of people starts killing another group foreign governments have every right to intervene. It's not as if its okay to kill your neighbor just because he's the same ethnicity as you.
Granted, I recognize that foreign intervention is not always good- I doubt the Vietnamese are better off now then they would have been had France, China, and the US stayed out of the area- but none of those countries did anything wrong when they aided their allies.