There's no way to completely summarize what Horowirtz concluded in this short space, but let me highlight some of the standout points I found when I read it.
1) Southern identity is sometimes tied to "The Lost cause"--that of the Civil War and independence--and that this sometimes defines what it is to be southern. (I agree, but of course it's more complex than that)
2) There is a huge social, economic and racial gap between blacks and whites in the South, even today. Horowitz talks about feeling like he was the enemy, as an outsider, and Jewish, talking to southern whites, and as a white man talking with African-Americans. (I agree and think most of the country doesn't realize how much of our racial legacy, and the legacy of slavery, still exist in the South)
3) The South is easy to dismiss as a bunch of rednecks, "crackers", or uneducated people, but the South is a society made up of complex people and views, and there are no easy answers, no clear "right" or "wrong". (I agree completely)