There are certain precepts and simplifications we all make in our lives simply for practicality's sake.  We accept the word of the doctor because we can't all go through medical school, we walk down the street with the understanding we won't be randomly murdered, and we keep the suffering of much of the world as an afterthought.  All situations we cannot really control, and while preferrably we could do better, it's just not practical.

This tendency has led to an unnecessary creation of convenience that oversimplifies the nature of crime and immorality to an us versus them mentality.  It would be much easier if we could simply say that a murderer is simply evil, therefore kill him, but the concept of "evil" is immature and baseless, and under no circumstance should this precept be apart of the philosophy of the criminal-justice system.

The idea is that some people are simply "evil" -- that they have no moral inclination and do everything with themselves in mind just because they were born that way.  The connection between others' suffering and one's own isn't a simple on and off switch.  Despite not being a psychology as per the earlier example, I think it is safe to say that upon evaluation of the cases of criminals, there's an entirely different underlying cause than he wanted to be mean.

For example, a high incidence of child predators were sexually abused themselves.  It would be nice if we could simply dismiss them as evil and lock them up.  However uncomfortable it may seem to the individual, the goal of the criminal-justice system needs to be rehabilitation and not retribution.  What harm was done by the criminal's hand can at least be partially atoned for by being a positive member of society after reformation.

This does not discount personal responsibility, or that there are acts that are truly selfish, but these are not acts perpetrated by a naturalistic tendency toward sociopathy; there is an underlying sociological and psychological influence that cannot be ignored.

The lack of the concept of evil does a lot to the vindictive side of people, as revenge is not a solution and harm for your own satisfaction is not justice.  Without the concept of evil, death as a punishment is unjustifiable.  Without the concept of evil, war becomes a tragedy.  Without evil, we must come to grips with reality.

Have you ever heard the phrase "being the bigger man"?  It's the act of placing the betterment of the group or situation over your own personal desires.  This is supposed to be considered a virtuous act, yet more and more it is scrutinized.  What better example of being the bigger person could it be than to accept that it is better off, if possible, to have the perpetrator of a horrid act be able to transition back into society.  To admit that even those being the worst offenses toward humanity do in fact still carry the capacity for good.  It's not easy and it's not dignifying, but it's right.