Sorry Mahdi, but there’s nothing new in this idea at all:

He started out wanting to track social capital over time and in
different communities across the US. What he wasn’t expecting to find
was a negative link between ethnic diversity and social capital. Put
crudely, the more ethnically diverse the neighbourhood, the less likely
you are to trust your local shopkeeper, regardless of his or her
ethnicity. He warns that, however uncomfortable this conclusion might
be, "progressives can’t stick their head in the sand".

But the
killer punch of his research is that diversity not only reduces social
capital between ethnic groups but also within ethnic groups. Diversity
leads not so much to bad race relations as to everyone becoming more
isolated and less trustful. In the jargon, it kills off both the
"bridging capital" between different groups and "bonding capital",
which is the connections among people like yourself. Putnam calls it
"hunkering down" as people withdraw from all kinds of connectedness in
their community. And what follows is a long list of negative
consequences, which include less confidence in local government and the
media, lower voting registration (though higher participation in
protest), less volunteering, fewer close friends, lower rates of
happiness and perceived quality of life and more time spent watching
television. It affects almost all our relationships, from the most
public to the most intimate.

For years people have been pointing out that this applies to welfare societies. The more culturally (some would say racially or ethnically) homogenous a society is the more likely they are to support a comprehensive welfare state. Because when people look at those receiving the help paid for from their taxes, they see themselves.

Nothing very surprising about it either. We’re humans, you know, tribal animals.

So where’s the surprise?