Well i tend to agree with you, they have to want to be rehabilitated firstly. and i think forcing it on them in those circumstances would only make them more resentful towards animals.
But maybe not in this particular horrific case, but there maybe some who can and could be rehabilitated, they do try this here for other crimes against humans, and in some cases it works.
Still LOCKING THEM AWAY and throwing AWAY THE KEY, could and would not be good enough for them in my personal opinion, in this particular case.