[j. earl carter]

The idea that people should use deadly force only to defend their lives is rooted in English common law, author Richard Maxwell Brown says in No Duty To Retreat: Violence and Values in American History and Society. Another common-law principle, the “duty to retreat,” requires people to avoid potentially deadly confrontations. The principles apply in many U.S. states. The duty to retreat generally doesn't apply in a person's home

http://www.usatoday.com/printedition/news/20060321/1a_bottomstrip21_dom.art.htm

[Durus]

"The idea that people should use deadly force only to defend their lives is rooted in English common law"

Someone can die from being punched once if the right spot, even if it's pure bad luck and not skill. While you may be willing to risk it I don't think you should advocate that everyone takes that risk. Further while you state that "Duty to retreat" is a common law principle that dates back to whenever I can think of many historical accounts that directly conflict with that theory.

The only people served by "duty to retreat" laws are criminals.