Restated - those places with a homogeneous Western Culture were most trusting, with the highest level of social capital, than those places with any dilution of that Western Culture.
And what culture is the left trying to destroy? Yep.
Notice he didn't find any "homogeneous" places that weren't "white" (ie, Western Culture) that had a high level of social capital. So, if it was a matter of homogeneity - some all black neighborhoods would have a higher social capital score than a mixed neighborhood.
I'm certain that the researcher would discover that the "social capital score" would be directly correlated to the "Western Culture score" for the area in question.
What needs to be added is that trust isn’t universal among “whites”, either. There is a significant range of trust between different white ethnicities and it drops off quite a bit even in Eastern Europe and in the Southern parts of Europe, for example and there are groups like the Irish “Travellers” that test the tolerance of those around them.
You also need to notice that there is a tremendous amount of trust in Japan, which is not quite “Western Culture”. I would argue that it rivals, if not exceeds, the trust and social capital in the United States. The amount of things that get left out in the open in Tokyo without getting stolen and things done as a matter of trust was mind-boggling when I lived there. Further, if you look at immigrant black communities from the Caribbean and parts of Africa have substantially more trust than urban African American communities.
So I agree it’s a matter of culture as well as homogeneity but it’s not just Western Culture and it’s probably counter-productive and unnecessary to invoke race at all, even as a proxy for culture.