Indeed, I think that to look on this account without feeling the compelling need to exact ferocious retribution is to deny one's own humanity. Some things need to be punished, not as a deterrent to others because they are probably beyond deterrent, but as proof that we are distinct from them.
He may deserve death, but society should not be the ones to administer it. For our sake, not his.
It has already been posited that it's a bad idea to sentence with emotion, and for my money that's an undeniable truth. In any case I'm sure we all agree he should not be let out, much less have his sentence reduced, and that question is much better place on which to focus attention, especially since there is no question of his guilt.