No less significant is the intellectual outlook of the rank and file in the communist and fascist movements in Germany before 1933. The relative ease with which a young communist could be converted into a Nazi or vice versa was well known, best of all to the propagandists of the two parties. The communists and Nazis clashed more frequently with each other than with other parties simply because they competed for the same type of mind and reserved for each other the hatred of the heretic. Their practice showed how closely they are related. To both, the real enemy, the man with whom they had nothing in common, was the liberal of the old type. While to the Nazi the communist and to the communist the Nazi, and to both the socialist, are potential recruits made of the right timber, they both know that there can be no compromise between them and those who really believe in individual freedom.
--FA Hayek