jock I don't think anybody is born evil.
But there is the age old debate, nature over nurture which in all this time nobody has really got to the bottom of.
I do believe some people have traits that make it more acceptable to them to take part in heinous crimes.
More prisoners than we probably can even imagine May have some form of SN. What we have to be careful is that doesn't become the basis of an excuse.
I once read some where that children form the sense of what's right and wrong at the age of seven. You and I have a sense of what's right and wrong. If you get to be an adult and still don't have that sense and commit terrible crimes, you have to be taken off the streets to protect the public.
Some people do rehabilitate.
Some people wont and those people will have a team of professionals ensuring, or should be, that they stay off our streets away from our vulnerable.
Your right some may even have mental illness, arsonists, phycopaths, with all your good will these people can't be saved. So we have to protect the pubic.