There seems to be a few countries that get on pretty well by avoiding the vengeance based justice thing. I've read quite a few things about how Norway handles these things and they don't seem to have issues dealing with violent crime even when it happens (they also seem less prone to flying off the handle when bad stuff happens).

I like you're post, irregardless.

There's a difference between being a murderer and being responsible for a death.

IF it is actually murder as we understand it, then yes, in my opinion they have forfeit the right to have a life of their own continue.

Edited.. spooling as usual.

Yes, doesn't undo the killings.

Anyway where would you stop? Killing the one who killed the one who killed the one ... who killed somebody? Nobody left in the end.

Depends which religion you adhere or don't adhere to.

On a philosophical level, willingly killing the killer makes you a murderer too, so you should be killed as well I guess. And the guy who killed you, etc. The last one should close the lights and commit a ritual suicide.

GOG.com

I find it disturbing that there are so many Punisher wannabes in this thread... Seriously, if you kill a murderer, you are a murderer. If you think a murderer should die because he or she is a murderer, you are not so different from a murderer. Two wrongs don't make a right. The death of a murderer, will not bring his or her victims back to life. The families of those victims will still have to suffer everyday. Killing is wrong, okay?

It's ok as long as you don't get caught. :))

Let me be somewhat facetious here:
One
Two
Three

While I do agree to a certain extent with the batman metaphor, I have to disagree because its scope only applies to Western society, and not even the US. For the batman metaphor to be completely right it assumes there is a level of morality that is universally agreed upon, and that just isn't the case. In the US, it is legal to kill someone in defence of your person and your property or in defence of another person or their property. It is also legal for the state to kill you so long as you are found guilty of murdering another and it is legal for you to kill someone who is attacking the state or whom the state deems potentially threatening. In some regions of the world it is legal to kill someone for sexual crimes ranging from rape to adultery, and in more primitive societies it is acceptable to kill for a huge number of reasons ranging from women to land to rivalry.

My point is the cultural context plays a huge role not only in the legality of murder but also in its psychological effects. I've seen a lot of people mention guilt, regret, morality, or spirituality in this argument but these are all cultural constructs and not applicable universally. A minority of military personnel experience these issues even though they have committed murder because it is culturally acceptable and even lauded in our own and most societies. Having 'blood on your hands' is a common allegorical phrase that is popular in theatre but really holds little value in reality.

So is it wrong to murder someone who has murdered someone? In the cultural context of Western Liberalism, I would say no. We do not kill soldiers returning from war even though in the countries from which they are returning they're often considered murders. Nor do we kill someone who killed a burglar that threatened their property even though it was not clear they were deserving of death. In the US, someone who murders another in cold blood is entrusted to the state for their execution, but do you trust the state to even collect your taxes properly let alone be the moral compass? I do not, nor do I believe anyone should be entrusted with that purpose.

There are those who will say justice requires the death of another in return for murder but I don't want to get into that argument, perhaps others can expand or you can read the Republic, just for a taste of how convoluted that debate can get.

Edit: typo

Karma is a bitch ;)

To stop further killings? To stop a person who has killed plenty already? Sure why not.

Yes.

Also, the death penalty is wrong as well. The idea is good, but giving people the power to kill another person for crimes is wrong.

It's all wrong.

We live in a time of plenty, where the main factors of natural conflict have been removed, need for sex and need of food. But when these are in short supply, and someday they will be if the world population keeps growing, what will happen to the standard of morality which is currently held as a certainty?

You mentioned child abuse and domestic abuse but these are very rarely mentioned in the Bible or antiquity and it was not until 200 or so years ago in the West that they were even considered through a moral lens. In fact the Bible says you should kill your child if they won't obey! Oh, how morality has changed! While viewing through an anthropological point of view may lead to certain blindness, it also puts things into context and makes one realize that morality is a dynamic beast, and what is moral at present will probably not be as moral in the future. Since we are far from agreeing on a universal standard of justice it stands to reason that our current perception will inevitably change.

So at the OP, what is considered murder today might not be murder tomorrow so you should let your current standard of legality and justice dictate your opinion, while always being prepared for the certain change.

Edit: Don't get me wrong, I'm not advocating murder or child abuse in fact I'm against the killing of any people for any reason, but I don't want to let my personal perception of those things get in the way of argument. My past experience greatly contributes to my current opinion of morality but it's best to leave those aside for the sake of objective argument.