The brain is a physical thing, and the brain is what makes us do stuff, like think or act. I'm relatively certain that if we stick around long enough, we'll figure out what parts of the brain cause anyone to do anything, and thus every action, from eating cereal to stabbing puppies, will be subject to a "I couldn't help myself" kind of defense. That's fine with me, but we still need to figure out what to do with the people who "choose" to skip breakfast in order to stab more puppies.
Certainly, we can sympathize with them if they truly could not help themselves, but the fact remains that we'd like to have as few puppy stabbers running around as possible. "3 hots and cot" seems like the best option to me; isolate them from the society that they can't fit into for that society's benefit, but don't go out of your way to make life hell for them either. It'll be a long time before that view is accepted though. We really want to believe that the puppy stabber is a bad person who must be punished, and that we would have chosen differently given the exact same brain.
Or, I'm full of crap and scientists will soon discover FreeWillnium, a substance not subject to the laws of physics, found in the brains of all humans and sufficiently cute puppies.