Better they rot then live and cause us issues, misplaced empathy got us into this mess after all, they're my enemy and thusly I look at them as such, it doesn't really matter the "why" on a case by case.
They know no redemption on their side. It is not an option that exists in Satan's camp. I don't believe they were created purely to become an abomination. The empathy I feel towards them is the same as the junkie or others trapped in bondage. I am not trying to be patronizing to you, but it's difficult for me to explain. It is the desire for them to break out of this for their own sake plus mine and society at large. In a way it's like watching an animal fumble between houses and traffic and hope that it just had a head injury rather than rabies because you know what's coming next; I will not be feeding or actively caring for the animal simply because I hope it doesn't die of rabies.