This is exactly why I don't care for guns. You are basically saying flint that a messed up paint job is reason for murder.
Like Soth said, both were at fault. But what you are advocating is that as long as one person was at fault no matter how minor or major the "crime" was, murder is acceptable. That's not justice, that's revenge. I also take it that you've never heard of a misdemeanor. A lawsuit would've been perfectly acceptable.
Do me a favor and stop talking. I'm still trying to convince europeans that there are intelligent Americans. You're not helping my case =/