It is not the necessity to make an arbitrary choice in itself but precisely the fact that your choice will necessarily be arbitrary that terribly complicates the matter. There is no reliable criterion on which your choice can be based. Why is there none? Because the proud humanity of today ‘has done with the Bible,’ so to speak; it has voluntarily rejected all systems of old religious beliefs as insufficient, erroneous, or obscurantic. Those belief systems might have been obscurantic all right; and yet, having done with them, we as humanity are left with no moral compass at all. Science fails to provide us with reliable knowledge of what is Good and what is Evil, just because the very terms of ‘Good’ and ‘Evil’ are unscientific.
(Why are they?) So away with morality, let us move on from the Bible, let science and rationality be our new compasses! The tiny problem is that the choice between two groups of people whose views contradict each other is a moral one: it cannot be made reliable by applying the criteria of rationality, pragmatism, or efficiency. You see, Mr Joseph Goebbels who was a minister of propaganda in Nazi Germany thought it very ‘rational,’ ‘pragmatic,’ and ‘efficient’ to finally solve the Jewish question by establishing the Auschwitz concentration camp and other similar means. Every time you start talking of ‘eliminating’ a person you must be prepared to be ‘eliminated’ in a similar way, because your unique personality, your race, or the group you belong to may also be found ‘inefficient,’ ‘irrational,’ or ‘obscurantic’ one day or another.