Lol, at first I thought you were yelling at me for saying "Muh underage."
But I agree. If you do crime above a certain level, you waive your right to claim childhood innocence. It'd be one thing if it was manslaughter, where someone doing something stupid or mundane and an accident happens and someone dies because of it. The guilt alone would probably eat you alive if you have a soul to burn. But willfully and with complete cognizance of what you are doing and doing it anyway? Yeah, no. Tried as an adult, half the maximum punishment as a minimum without bond or bail.
Same with the little rapist niglets, spics and so on. And their parents or guardians are punished too for allowing this shit.
Creatures like this or the ones you described don't have a soul to burn. They don't feel guilt. They are evil and should be treated as such.