As promised, a few comment on Richard Rhodes book. Why They Kill is an exploration of the career and ideas of a criminologist named Lonnie Athens. Athens grew up in a very violent home and found himself drawn to the field of criminology when he discovered there was such a thing during his college years. Athens' immediate reaction to the prevailing theories about violent criminal behavior was that they did not at all match up with his own experiences and observations. Violent criminals, in his experience, did not "snap", go crazy or otherwise act irrationally when involved in violence. They were simply acting on the basis of their personality and evaluation of the situation they were in.
While countless studies had been conducted in sociology collecting data sets on the "factors" associated with criminal acts, Athens thought this was entirely the wrong approach to the question. In his mind he felt that the best approach was to do intensive interviews with violent criminals and find out if there were common patterns in their backgrounds and in the way they perceived their reasons for acting violently. He carried out this research in various prisons and made the startling conclusion that there was a specific pattern to the background of every single one of the violent criminals. Each person went through specific stages of development, so to speak, on the way to developing a violent personality. Athens called this process "violentiztion". I'll not spell all these out, since I think you should read it for yourself.
Athens academic career was not successful though. His rough background and his non-conformity to prevalent sociological methodology put him at odds with many of the people in his field. His books were not accepted by any american publisher, though they were eventually accepted by the british publisher Routledge.
After spelling out Athens' research, Rhodes goes on to examine whether Athens' scheme could be seen as applying more broadly. He looks at several notorious cases of violence which had already been examined heavily by other journalists such as Mike Tyson and Cheryl Crane (Lana Turner's daughter). Additionally he looks at the history of child rasing in Europe and its possible connection with the violence which had been so common before the 18th century. Murder rates in rural medieval Europe, for example, were quite comparable to those in the worst 20th century cities. THe process of violentization always has as its first step brutalization. This could include either being personally beaten or witness horrible violence done to another person. In examining historical work on child raising norms in european history, Rhodes quotes one scholar as saying he could not find a single documented example of a child who was NOT beaten before the 18th century.
Rhodes also goes on to look at violence in warfare and its relationship to the training methods used by the military. Again, there was a lot a fascinating material here which I will encourage you to read for yourself.
Towards the end of the book RHodes turns his eye to a subject which Lonnie Athens had not discussed in his writings: conservative christianity. Rhodes mentions several popular christian books on child raising and scorns their model of seeing children as creatures of evil whose wills need to be "broken". I found this section disquieting. The discussion of the relation of christian child raising and violence could certainly have been nuanced quite a bit more than it was, but on the other hand, I think it is not at all far fetched to suggest that many violent parents see justification for brutalizing children through certain fundamentalistic beliefs and teachings.
Anyhow, this was easliy one of the most interesting books I've read in my lifetime. Can't recommend it highly enough.