“Once I have refused to press that button because of Heinz, I can never press it.”

Source: Christopher and His Kind (1976), p. 335
Context: Suppose, Christopher now said to himself, I have a Nazi Army at my mercy. I can blow it up by pressing a button. The men in that Army are notorious for torturing and murdering civilians — all except for one of them, Heinz. Will I press the button? No — wait: Suppose I know that Heinz himself, out of cowardice or moral infection, has become as bad as they are and takes part in all their crimes? Will I press that button, even so? Christopher's answer, given without the slightest hesitation, was: Of course not.
That was a purely emotional reaction. But it helped Christopher think his way through to the next proposition. Suppose that Army goes into action and has just one casualty, Heinz himself. Will I press the button now and destroy his fellow criminals? No emotional reaction this time, but a clear answer, not to be evaded: Once I have refused to press that button because of Heinz, I can never press it. Because every man in that Army could be someone's Heinz and I have no right to play favorites. Thus Christopher was forced to recognize himself as a pacifist — although by an argument which he could only admit to with the greatest reluctance.