Good points all around, but I have to believe that moral justification for an act does not extend beyond the situation in which one is in. I can understand the idea of a Mad Max-like anarchy, but even then, I don't think going out and slaughtering the *** who hurt you or your friends/loved ones is really going to solve the problem. You have the right to defend yourself and your family if attacked. That's never been a problem for me, and I am Christian myself. Jesus said to love one's neighbour as oneself, to forgive the sins of others, etc. He didn't say go out and torch the entire neighbourhood of the guy who did you wrong (a la the Punisher reference). That's just wrong. In fact, that's just sinning right back at the guy who did it to you. It's not a solution, it's just violence.
Heck, look at it without the Christian motif. Do you have the right to hurt someone after the fact? No. Your life is not in danger. The damage has been done. The best way to stop it from happening again is to promote the values of tolerance, love for one another, etc. that will prevent people from acting like psychos. The law exists for the purposes of distributing justice, yes, but the goal of government, and of society, should be to educate people to the point where the government and the law no longer needs to be enforced. Instead, people should be trained to respect the idea of the law in the first place. Not easy to do, sure, and hard to make practical... but that doesn't make it right to take justice into your own hands. No individual is omniscient or all-powerful. We don't know enough to judge other human beings, and the law is, at best, a meager attempt to put limits on bad behaviours and punish wrong-doing. Wrong way of going about it in my opinion. You have to gradually remove the violent tendencies from the society, which takes more work... so of course, no one wants to do it!
To use a good quotation that might reflect my opinion just as well as this whole rant: "Many people who have lived deserved death, and many who have died deserved life. Can YOU give it back to them?" (Gandalf to Frodo, in the Lord of the Rings, the first movie) We don't have the power or the authority to make the decision to take the life of others, justice, into our own hands.