this was really amped up during the presidential campaign where young and old, & white and black became very divided even though we would call one another brother and sister. Even afterward the sense of fear and trepidation from far right wingers was disconcerting. That will continue to be an issue within the "kingdom of church" culture. These next months and years with a new president will be very interesting, especially if it goes well!
United By Faith is a terrific book dealing with the history of diversity with a cultural perspective on the Day of Pentecost. The primary idea is that the chuch, that's right I said 'chuch', should model this embracing we're all praying for. Historically the 1st and 2nd Great Awakenings seemed to impact the embracing between whites and blacks. It's a very interesting read blending the spiritual and sociological factors that make up the church at large.