The pro-social ideal draws strongly on thoughts about social capital. Wonky types have been talking about this for a while: here are useful government papers from 2001 and 2002 (pdfs).
Social capital guru Robert Putnam has been talking about immigration recently. Apparently, ethnic diversity does reduce trust and social solidarity. I find other trends more worrying. In 2003 the average British commute was 35 minutes. Today, it is one hour five minutes. Nick Paumgarten considers the implications in the New Yorker.