Stanford Prison Experiment Ethical?

Even though the Stanford Prison Experiment went to the extremes, I do believe that the experiment was ethical. It showed even that good people with a good mental stability can get so much into a role that they will start to believe that it is true reality. The students that had to play the role of the prisoner began to act like a prisoner, and the students that played the role of a gaurd began to act as a gaurd. How do I put this... Instead of playing the role, they ended up becoming the role and thinking that this was reality and there was no way out. The experiment that was supposed to last 2 weeks ended up only going on for less than a week. I think that an experiment like this can help us if anything like this was to happen again, like Abu Ghraib, and so we can prevent and stop it from occuring again.