Josef Mengele, an SS physician infamous for his inhumane medical experimentation on prisoners at Auschwitz, is in this film a character intent on furnishing the 95 Hitlers he has cloned with Hitler’s own background. Crucially, Hitler’s father died at 65. So too, Mengele, reasons, must the adoptive fathers of the boy Hitlers. Otherwise, they might not turn out like Hitler. The ethics of Mengele’s task—killing 95 innocent 65 year-olds—is clear. When Ezra Lieberman stops Mengele in his tracks, the question turns to the ethics of killing the 95 boys so none of them will grow up to be another Hitler. This is a much more interesting ethical question, and the narrative—and film as a medium, moreover—would be fuller had the script been deepened to make the question, and thus the ethical and ontological dimensions, transparent for the viewers.
The full essay is at "The Boys from Brazil."