I think you'll find that they actually have legitimate reasons for doing what they do that make their actions understandable. I won't go into that here though. I might make a thread soon.
Also, let me ask you something:
Do you think that just killing these people will change anything? If you just immediately write their actions off as unforgivable and kill them, how will you be able to further understand their motives? You see, these people become the way they are due to their own experiences, and they often have very similar backgrounds. Sometimes they legitimately don’t know better. If we took the time to be nice to these criminals, to try to understand them, we would be able to help them understand the implications of their actions and hopefully change themselves for the better. Killing a killer is the cowardly thing to do. What reason do we have to fear our own kind?
We are all humans. If we collectively tried to be more empathetic, I believe that we could eventually achieve peace.