Why is that "the thing to do?"
Because that is how civilized countries operate.
Because it distinguishes us from the perpetrator.
Be it is what civilized nations do.
Because, Jack, civilization is about the struggle between our capacity for brutish depravity and moral order.
We loathe this man because we recognize his act was cruel, brutal, and depraved. That is good. Brutal depravity in dealing with him makes a mockery of our moral reasoning.That is bad, Jack.
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.
Because, we're better than he is. At least I am. Given your posts, you're in question, but I know that I'm not sinking to an inhuman level.