“If some men attempt to survive by means of brute force or fraud, by looting, robbing, cheating or enslaving the men who produce, it still remains true that their survival is made possible only by their victims, only by the men who choose to think and to produce the goods which they, the looters, are seizing. Such looters are parasites incapable of survival, who exist by destroying those who are capable, those who are pursuing a course of action proper to man.”