What's driving Repugnantans?

The author of this article finally figures out what it is when his Repugnantan relative flatly tells him. They're discussing the horrors of some people's lives and he asks why his relative doesn't feel empathy for them. Her response is telling: "Because it wouldn’t directly affect me.” That is the scope of their concern. Had the author been familiar with Kohlberg's work he would have discovered this much sooner. It is a matter of moral development, or a lack thereof.