Sowell wrote about violent crime, which includes murder but is not restricted to it. Second, your link does not disprove anything Sowell wrote. As for thet 2012 murder rate, try the link below. It's an article stating that Washington, DC, is on pace for fewer than 100 murders in 2012, the first time since 1963 that the rate was below 100.
What was that you wrote about ignorance?