Stanford Prision Experiement - Is it really creative evil?

I once watched a movie having a similar outcome; The Felon.  A honest, hardworking father and husband; Stephen, mistakenly killed a man who was burglarizing his home. While chasing the intruder he made one swing with a bat, killing him. He was convicted of involuntary manslaughter and sentenced to three years in a maximum security prison along side some of the most violent offenders, where the guards used brutality as a means of control.  Outside of work, the guards lead normal lives with wives and children. Each day spent in prison environment seemed to rendered Stephen and the guards more desensitized then the day before.  For Stephen, normal life experiences in society couldn't prepare him for daily life in a violent prison.  He soon became a product of his environment. I agree with the critics of Zimbardo.  Any experiment rendering participants emotionally, physically and psychological scarred is not worthy to be called research and is unethical.  Though the experiments were conducted on a voluntary basis, it should have been stopped immediately  as soon as these issues surfaced. It's not worth the damaged caused.