The question is why and how the decision is made to avenge the audacity of the other stupid driver. Almost one year ago on this page I posted the subject "Evolution" asking if we are as highly evolved as we are led to believe that we are. My general thesis in that post was that we are not highly evolved and still operate with the basic tools of the early cave dwellers. We are, as societies have changed, controlled by social convention, but it seems to require only a small incident to get us to revert to a very basic instinctual reaction. It is only a blink of the eye in cosmic time that we have been "civilized" with rules, laws, and mores. So. I continue to come down on the side of nature with regard to aggression and violence.
But, there are divergent views and the question will probably not be answered in our lifetimes. I did some hunting around for a balanced look at the issue and found a 2002 article on Serendip.com written by Sarah McCawley at Bryn Mawr College here. Some of the footnote references have not been updated but it is a good start in understanding both side of the issue. I am always open to a change in thinking, and welcome comments. But right now my serotonin level is up so I will stay off of the roads today...