"The reason why neighborhoods integration and cohesion cannot co-exist is based on how humans form relationships..."
"...people usually build relationships with others who are closer and similar to themselves, be it through race, religion, social class, etc."
STUDY: The Downside of Diversity
http://www.boston.com/news/globe/ideas/articles/2007/08/05/the_downside_of_diversity/?page=full
"...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."