The Annihilators (1985)

When a gang terrorizes a neighborhood, one of its members, who is a Vietnam vet urges them to fight back but they are either too afraid or feel that they are not trained to. When the gang learns of this, they go to him to get him to shut up and when he wouldn't, they kill him. And the police are either unable or unwilling to do anything. One of the vet's Army friends, Bill, who comes to the funeral, and is told by his friend's father what happened and is asked to teach them how to fight. Bill then calls three other friends and they teach the citizens how to fight. When they learn who killed their friend, they decide to get back at them, and when they learn that the gang is a courier for some drug dealers, they decide to hijack their shipment, only trouble is, the shipment is extremely large and the gang is prepared to burn the whole neighborhood to get it.