My conclusion is that humans encounter a barrier of confrontational tension and fear, when they are faced with committing violence against another person; and this emotional barrier either prevents the violence from happening, or makes people perform very badly. We can see this because the same policemen or soldiers who can shoot well at targets on a firing range, will miss their targets, fire far more bullets than necessary, and show others signs of being under great emotional pressure when it is a real situation of violence. 
Where does this emotional barrier come from? It cannot be merely that it is part of modern culture which inhibits violence. We see people in tribal combat, from anthropological films, behaving much the same way: a few men from a large crowd of armed tribesmen will run forward toward the enemy, throw a spear – usually very inaccurately, and quickly run away, while the rest do no more than shouting. Yet these are the same people who culturally express great satisfaction when one of their enemies happens to be killed. I conclude that the barrier of confrontational tension is deeper, and comes from basic characteristics of how humans interact with each other. 
In my previous book, Interaction Ritual Chains (2004), I show from micro-detailed evidence that when persons are bodily near each other and focus their attention on the same thing, they tend to fall into a shared rhythm. They will take on the same micro details of the rhythm of speech and body movement; the emotional mood between them becomes stronger. They become mutually entrained in each other’s emotional and bodily rhythms. I call this the mutual-focus/emotional entrainment model. It is a development of a theory – now supported by modern micro-empirical evidence – that was formulated by classic sociologists such as Emile Durkheim in his theory of religious ritual, and Erving Goffman in his theory of the rituals of everyday life. Successful interaction rituals bring social solidarity, and are very attractive to individuals because they give them emotional energy – confidence, enthusiasm, feelings of strength. 
Thus we can see that the two forms of interaction – interaction rituals producing solidarity, and violent confrontations – are antithetical to each other. Of course people can have many motives to conflict with someone else, and they may be very angry and intend to cause violence. But when they come closely into the confrontation, they become caught up in the human tendency for entrainment with the other person. So they are in a situation of conflicting emotions, and quite literally, conflicting tendencies within their own bodies. It is this bodily self-conflict which causes the tension. Because persons on both sides of the conflict usually are feeling approximately the same amount of tension, most of the time they find some way to avoid fighting, or to bring the conflict to an end very soon. If we look at videos of fighting – which are now posted on the Internet – we see that fights are almost always very short, and people soon find an excuse to end. For more serious fights with guns, in a large percentage of the time the shots miss their target, even if fired from very close. It is the strong tension which is causing them to miss.
In order for violence to be successful, the situation must allow a pathway around the barrier of confrontational tension. In the book, I describe several of these pathways. The most important of these is finding a weak victim – and that means an emotionally weak victim, in that immediate situation.

You suggest, also in an article published in Foreign Policy, that Islamic suicide bombers belong to the middle class, whose members are socialized to behaviours and dispositions (such as self control, a physical aspect over and above suspicion, etc.) that are more suitable for committing violent suicide acts. Can you explain in more depth the correlation between this type of violence and middle class culture? Are the motivations of a suicide bomber independent of class interests? If they are, to what extent?
 

 
One of the most unusual ways of circumventing the barrier of confrontational tension is to pretend that there is no conflict, until the very last instant when the violence is unleashed. Most violence starts with gestures, threats, angry noises, or other ways of signalling danger. In fact, this signalling is mainly a way to try to intimidate one’s enemy, so that they will not fight. Suicide bombers take a very different pathway. They pretend they are normal citizens in a very routine situation. This is an unusually effective mode of violence, since a suicide bomber gets right up to the target, and does not miss – as most other kinds of violence usually do miss. In this respect, a suicide bomber is like a professional hitman – a contract killer, who uses the same technique of maintaining a clandestine style of normalcy, until he can put his gun a few inches from his victim’s head. 
In this sense, the clandestine approach is not so much an intrinsic part of middle-class culture, but rather a sophisticated technique that was invented and spread through social networks. We see that the professional hitman has a similar technique, although he is usually not middle-class; but he is much better at his job than the usual working class gang member, who engages in noisy bluster and thus is not really very effective, except in scaring others. But once the technique is recognized by political groups, it becomes recognized that middle-class persons are the best at this, and the more respectable the better.
That is why women are particularly good at suicide bombing.
Here it is not a matter of class interests, but merely of class interactional styles. Most middle-class persons are not ideologically oriented towards suicide bombing, or indeed any other kind of violence [except maybe to see a fictional version in films].
Ideological movements are not very closely related to class interests, and the most successful movements – such as militant Islamists – are good at recruiting people across class lines.