Psychopaths lacks any sense of conscience or morale and they are capable of hurting anyone to achieve their own selfish goals and fake emotion while they don't have any.They cannot be helped because their psychology is like...eh, I have to say, non human, they have the appearance, but no substance.But they have free will, nobody forces them to hurt people and they are perfectly sane if they do not have another mental illness, so that's why I think we should never have mercy on them when they do horrendous crimes.So what we must do according to you?Leave them until we find a cure for their soulessness?They are sane, but completely amoral.

"Evil" is the characteristic that defines them most closely.
That's why they're giving me creeps and honestly I think the world would be better if we at least locked them up all.
They have no compassion to others, no heart, no soul, but they are not insane.

When cure to this will be developed you will basically solve the problem of evil in the human race.
Normal people do evil, but they have boundaries.
Psychopath never has any such thing, if he killed your child brutally he will not feel absolutely anything, no regret, no nothing, that's why I hate them as abominations and a carcerous growth on any civilization.
Please do not have sympathy for psychopaths, because they are not capable of feeling anything.
A psychopath simply has no concern for anyone expect him and his immediate gratification.
Psychopaths appear as normal and most of them never do any really serious crime but they hurt people in many other ways.
They leave empty wallets and broken hearts and they infiltrated our human culture to than point when some of the psychopathical behaviors are actually seen as "competive" and "desirable" and moral relativism is seen as acceptable.
A sad, sad thing.
And a disturbing portion of the population are psychopaths.
I think that every civilization starts with a bit of good and evil because social civilization cannot be governed by evil.Only when flawed individuals that do not mind raping and murdering someone with a smile take control, a civilization can become truly evil but then it would destroy itself due to wars, because everyone will want to have the most and don't mind killing other do get it.

You didn't understand me, I am saying that because you simply cannot have long lived evil civilization, because everyone would care only for himself, not for the civilization, but just him, him, him ,him....
Egomania and narcissm are the basis of evil.
Psychopath is not a madman in the common sense of that word, just a being in which there is no good and evil has overtaken.
But yes, they are ill because they are not capable of feeling any good, it is not their fault.
But you can judge them morally because they are still sane.

Perhaps this is the sad explanation for the rareness or nonexistence of really advanced civilizatiions, that psychopaths lie their way over and overtake, in turn start a period of massive wars that will go WMD and destroy the entire civilization.
Coincidentally this means that we will encounter many pre-WMD or our nowadays technology level civilizations, but very rarely those that survived this critical stage.
That''s because before WMDs there are no artificial means of how could civilization start a seft destructive fatal war.
And WMD+psychopaths at charge = bad news.

I am not taking about any poor people who hurt someone because they are insane or beliving that they are actually helping, but parasites that can sponge you off in a minute or worse.