The previous four values point to one that lies below the surface of the other four: respect. If members of a team don't care about each other and what they are doing, XP won't work. If members of a team don't care about a project, nothing can save it.
Every person whose life is touched by software development has equal value as a human being. No one is intrinsically worth more than anyone else. For software development to simultaneously improve in humanity and productivity, the contributions of each person on the team need to be respected. I am important and so are you.