Imagine the fear our ancestors felt in the night when wolves surrounded the camp. Now imagine that fear countered with a stiff lip and a sharpened point to defend against predators. Even the wolves learned to back off and fear that edge.
Throwing fists with someone is trouble enough, but whipping out your knife is an entirely different ballgame. No matter who started what, the fact that you chose to stab and slash your way out of a scenario makes you guilty of a litany of crimes.