Trends in manners and vulgarity determine future levels of violence in society.

What "jumps out" at your humble servant here is your politeness.  Manners count in human affairs, for manners blunt reasons for conflict.  It is when manners collapse or grow week that the potential for conflict escalates.  Our whole society is on a downward spiral because we now celebrate vulgarity in the mass media, instead of manners.  The result is shootings in movie houses over texting during film time, or shootings in parking lots over booming radio/CD music.  This is a polite, mannerly response, and as a result it blunts "edges" that could collide into conflict.