They are idealistic to the point where they have a completely unrealistic understanding of redemption or rehabilitation. To preserve the lives of the innocent, you must take the lives of those that are a highly probable & direct risk to them, that is obvious to me, it's just like the White blood cells/ T-cells doing their job. It's also obvious that if you allow people who are pre-disposed towards violent or depraved crime to rampantly outbreed those who are reasonable & civil, then you're going to have a bad time, it's going to create a hellish dystopia for the latter group.