The Trayvon Martin case is a wholly familiar one to residents of any major urban city. If you live in Chicago, New York or Los Angeles, then it's only a matter of time until an incident between a law enforcement officer, or more rarely a civilian defending himself, and a member of a minority group flares up into a citywide grievance theater complete with angry reverends on the steps of City Hall, women with stony faces holding up banners calling for justice and a media-driven debate about police tactics and racism.