John, Basically I agree with the premises outlined in the article.
I've run across this before and it is the result of other studies purporting to show the number of relationships of one sort or another that a human can(will) sustain.
In WWII we victors called them "Krauts" or "Japs". In Viet Nam they were "Slopes". Currently in the U.S. they are "Towel Heads".
I think that it is because we instinctively "sub-humanize" all those persons whose ideas are different from ours. This may well result from our inability to "humanize" more than about one hundred fifty entities. We do this rather selectivly and call them friends or acquaintances.
It's worth thinking about, particularly if you must make decisions that involve larger numbers of people. Stalin once said that one death is a tragedy, fifty thousand deaths are a statistic. (Consider the careers and adulations between "Jack the Ripper" responsible for perhaps a dozen deaths, and "Nikita S. Kruschev" responsible for about 500,000 dozen deaths.)
For instance in this modern world I am afraid that G.W.Bush, Pres. of the U.S., is unable to conceive of Allah as a real God.(God or Allah being the ultimate human in this case) Consequently he is unable to understand the concerns of the people to whom Allah is real. Therefore all persons who are not Abrahamicist in their outlook are not real people. Their extermination, and that of the GI's who also must die, doesn't matter any more than the extermination of the screwworm fly in Texas. Since they do not think (rationally like me

) evidently they are "sub-human".
A little education could go a long ways in this case. If people realized how limited in their outlook they "naturally" are perhaps (hopefully) they could change some of their most destructive behaviors.
Best wishes, M.