Because every time we, as a society, engage in publicly lowering our moral standards, it comes back to bite us. Every time we expose ourselves AND OUR CHILDREN (who will, one day, be "the boss of us") we cheapen the whole "life is valuable" theory. The shock value is diminished, life becomes cheap. When we punish acts of barbarity with acts of barbarity, we put ourselves on the same level as the killer. And that takes away our moral high ground.
This guy should die, no doubt about it. But, he should have a trial first....or maybe meet up with an "accident" during his upcoming incarceration. The State should at least have the appearance of equal justice for all.
"When we punish acts of barbarity with acts of barbarity, we put ourselves on the same level as the killer. And that takes away our moral high ground."
Moral high ground? How about holding people responsible for their actions and being brave enough to punish them when they break the laws. Don't do the crime if you can't face the consequence. How can a civilized person look upon the base wickedness committed and not see the need to exact full punishment? Maybe you're one of those people who can't feel compassion unless the crime happens to one of your family members.
It's really a matter of where to draw the line. European countries have the same beliefs that you expressed; and they don't have executions.