There are three motivations for having a criminal justice system. You've dismissed the least compelling of the three. In other words you put up a straw man and knocked it down.
> .... The best form of defense is to remove the deranged social
> conditions which give rise to deranged people, as this protects both
> the potential victims as well as the potential perpetrators.
The deranged "social condition" which gives rise to deranged people is called "life". Life is hard. Life may be harder in a capitalist system but it is nevertheless hard also in any utopian system you can imagine. Your wife falls in love with other people. Your father never really wanted you and doesn't love you. A reliance on back medication turns into an addiction. A freak accident removes your legs and leaves you incapable of playing the sport you love. Your uncle molested you as a child. LIFE IS HARD. Some people will be unhappy. Other people are just born jerks. Other people are clinically psychopathic. None of us are entirely rational.
Greed, jealousy and hatred are not minor problems that will be insignificant in a communist system. They are major problems that must be accounted for in any system.
Paul Prescod