The freedom of the South Vietnamese and our own freedom as well.
Veterans have first-hand experience with the issues, blood in the game, if you will. We know the price involved.
Bystanders don’t.
A combat veteran may have first-hand experience with the price that is paid in these military campaigns, but I don’t think it makes them any more qualified to render judgement about the wisdom of these campaigns in the first place. If anything, it’s probably the other way around.