Montresor thinks he has the right to murder Fortunado because he insulted him somehow. Without knowing what the insult is it is hard to say if Montresor was justified, but I seriously doubt he was. The insult was likely minor.
I would have to say that this type of justice might very well have been popular in the days when there was little or no law enforcement available. Like the justice of the old west, or in obscure villages or towns through history, justice was taken into the hands of ordinary citizens. This is not always a fair process, vigilante justice can go overboard. Just think of the Salem Witch Trials, there were no real lawyers or judges involved, just self-appointed crusaders working against the devil. It can be a scary prospective when you consider it that way.
Montresor takes revenge on his enemy Fortunato, an Italian cultural practice in Elizabethan times, and sometimes still popular now. It was an accepted practice to even hire assassins to get rid of your enemy.
This is a good discussion board question.
Personally, I would tend to say that individuals are not justified when taking justice into their own hands. I believe this only leads to big trouble for the one who is trying to execute justice. This is what our court systems are for (and yes, I know they are flawed at times), but then again, my sister is a lawyer, so I have been influenced by that a great deal.
Montresor is not justified for what he did. The reader never knows what wrong that Fortunato ever committed or if he ever really did anything at all to Montresor. He is an unreliable narrator and is clearly mentally ill, so he cannot be trusted. I have always felt that Fortunato probably did nothing to Montresor at all and that Montresor, much like the narrator in "A Tell-Tale Heart," simply found something irritating about him and his madness exacerbated that irritation to the point that he believed he had to kill him.
Yes, individuals are sometimes justified in taking justice into their own hands. However, that is rarely the case, and isn't the case here. To be specific, Montresor is unbalanced, and acting on a small slight (or several) to take revenge. He acts because only he sees the crime…because it doesn't really exist as a crime (as far as the reader knows). Individuals would be justified in taking justice into their own hands when the system is flawed. For example, if a terrible crime is committed, but the criminal escapes due to special circumstances (he's the friend of the king, for example, or he's a white slave owner in pre-Civil War America), there may be no other alternative.
I think that sometimes people need to take justice into their own hands.. For example, when you family is in danger.. Say someone breaks into your house and tried to kill you. Aren't you going to defend yourself or fight for your family? Sometimes you don't have a choice.