Surfing is an all-American pastime: think Beach Boys and people chugging kale shakes before heading back to the shore.
That's why it's crazy to see helicopters blasting away at the Viet Cong before touching down and letting their crew go surfing. It's incongruous, this most joyful American pastime dropped smack into the middle of a war zone.
When Col. Kilgore orders some of his soldiers to surf while they're still fighting the Viet Cong, they're hesitant. Explosions and gunfire are erupting all around. Willard wonders if this is such a great idea, but Kilgore's totally cool with it:
KILGORE: If I say it's safe to surf this beach, captain, it's safe to surf this beach. I'm not afraid to surf this place, I'm not afraid to surf this f***ing place!
But what about the Viet Cong?
KILGORE: Charlie don't surf.
Charlie was a slang term American soldiers used to refer to the Viet Cong. There's definitely a harsh tone of cultural superiority there. Kilgore gives himself permission to destroy the village just to clear out the beach for the Americans to surf. A good wave is worth a few dozen Vietnamese lives, don't you think?
This theme is the same as the one in Conrad's novel. Substitute Americans for Belgians and Vietnamese for Congolese, and you've got one "civilized" world power trying to impose itself on a country of people seen as inferior and disposable.