Our affinities fade with distance. Towards our immediate families, they are very strong; towards our extended families, less so; then outward ever more feebly to the broadest kinships (nation, race) and fictive kinships (religion, ideology, language, civilization). The math must be very complicated — much more so than a simple inverse-square law. I am sure that affinity can “pick up” strength for a while even as distance increases, just as there will be uphill stretches when walking down a mountain — that there are, for example, people who care more about their co-religionists than about their extended families. And I’m ready to believe that there are some individuals who honestly feel the same warm affinity for the remotest strangers as they do for their own kin. You might call those people “saints,” though personally I’d prefer something in the zone “half-crazy misfits.”
In low radius-of-trust societies affinity barely extends beyond kin. One can only imagine the difficulty Mussolini’s army recruiters had getting Sicilian peasants to fight for their country. Societies that can afford a more expansive view of the world typically have affinites that go out further. And of course the individual personality factors in. Joe may feel genuine distress thinking about the poor brutalized Congolese; Jane may not give a damn, or see why she should; and Joe and Jane might both be stalwart citizens, good spouses & parents, etc., indistinguishable in all the social virtues that matter.
In the broad generality, though, human affinities diminish with perceived distance (I don’t, of course, just mean geographical distance). Most people’s affinities are at effectively zero at some point well short of the Congo, as the Earth’s gravitational field is undetectable well before Alpha Centauri.
All this seems as obvious to me as 2+2=4. If there is something obnoxious in saying it aloud, I wish I could understand why.