The problem is that the Geneva Convention is not subscribed to by anyone other than state actors, some of whom don't even exist anymore. And even those are increasingly treating the conventions as optional. Groups like Hamas do not see themselves as under any obligation since they neither signed nor accepted the terms.
Which just makes my point. Your interpretation is your interpretation and others find other parts of the scripture to use in support of their aggression and violence. The crusaders happily massacred even other Christians while claiming religious authority so clearly there's some basis for disagreeing with your interpretation of that faith. Not to mention inquisitions and witch hunts.
Lets face it, religious authority has failed miserable at creating a peaceful world and secular philosophy isn't working terribly well, either. We are ultimately up against human nature, I think. We are territorial creatures who have taken that territoriality beyond geographical spaces to philosophical, political, and religious ones. No specific religious tradition can solve that problem because they are mostly part of the problem. Same with political philosophies.
I don't know how we can win this battle against our own nature, to be honest, but somehow there has to be a way. I just don't think citing scripture helps at this point because scripture is too tied up with how people interpret and understand it.
