"The Downside of Diversity"

In the Boston Globe, there's this long-ish piece, "The Downside of Diversity:  A Harvard political scientist finds that diversity hurts civic life.  What happens when a liberal scholar unearths an inconvenient truth?"  (A strange title, no?  What work is "liberal" doing?)  The piece is about Robert Putnam's ("Bowling Alone") new study finding that "the greater the diversity in a community, the fewer people vote and the less they volunteer, the less they give to charity and work on community projects. In the most diverse communities, neighbors trust one another about half as much as they do in the most homogenous settings. The study, the largest ever on civic engagement in America, found that virtually all measures of civic health are lower in more diverse settings."

I'd welcome any reactions from political or social scientists to either the piece or the study.  I came away from the article wondering if Putnam's study provides some support for my intuition that non-"diverse" institutions (e.g., some religious universities) are important in pluralist societies precisely because of their non-"diversity".