I think we should start with the people who are so ready to indulge in eugenics and not bat an eye. Next let's go with the rest people who think that they have the right to dictate people's worth to society on their own personal scale. Both categories, if they were serious, show little regard for human life.
I really don't like how you are seem to be referring to such people as "them" (that tone you have for "justify letting them walk around.") and how that could mean anyone that has a mental disorder which causes SOME people to commit atrocities. Particularly how it would make people avoid treatment. I understand how you'd want to keep those crazy potential psychos away from you and your tiny little world, but please don't talk from a high seat and decide who deserves to live and die or decide who can be free and who can live like an animal. Accept that there will always be people with problems and minds that don't function nicely in your world. When they go off, there's a decision to make in the courts based on their actions. Things they've actually done.
I admit I have a bias here as I am in treatment for a number of disorders, but I'm fine in sociaty when I keep up with my meds and such. I've worked very hard to relearn things and structure myself and have not committed any crimes. However, in your pipe dream I would have been raised so many red flags that I'm sure that I'd never see the light of day again. I'm sorry I'm not worth your chance, but I personally think that every human being is entitled to a chance and to be judged only by their actions.
No I probably wouldn't shed a tear if I saw you get hit by a bus, probably not even if you were a friend. Does that mean I'm going to push you in front of a bus though? As much as I'd like to rid the world of someone who'd think like you I respect your person-hood. Now if I could get away with it for sure ... I'd be very very tempted. In fact I could do it without really caring. I could even console you family pretending I cared. But I wouldn't because my beliefs require me to respect your right to live. My ability to do these things do not imply action.
Now what scares people I find is that they think that this means that I'm going to do it because I wouldn't suffer consequences. You seem to think that most people are only thinking of teh consequences or need them to keep you on the straight path. I'm not afraid like you are of doing these things. I personally find you a little weak for not being able to in fact. I for some reason don't do horrible things though. Most sociopaths don't act out on these things, or at least not to a great extent. See I live in complete freedom from the fear of consequences and feelings of grief that you do and I get to be moral only because I choose to follow what I know is right. Some sociopaths just choose to do horrible things anyway because it was an interesting choice. You think that stealing that bike will get you in trouble. I know I could do it and pull it off but I don't for some reason. Odd thing.
So at this point you should realize my point that sociopaths are simply more free. I personally don't think that they should be given much leeway in the courtroom because they naturally have MORE choice. Punishment will be ineffective anyway until you explain things on our terms, if we listen. Still, equal punishment must be served. Nothing more nothing less. You can never punish for things that have yet to happen for you are not a god and you cannot determine what I will choose or assume that I am immoral for my lack of inhibition.
When someone like you devalues me and people with similar conditions like this I do get rather ticked off. Thankfully with some time and learned self control I can say my peace, laugh, and tell you to go fuck yourself. =D