define justice.
"Punishment that brutal is almost the same as what he did to those childen."
exactly.
an injustice, when something is made wrong, when one person gets more than, or takes from someone else, there fare share. to correct this, that person must either repair the damage they have caused (plus intrest) or have a similar inequality exacted on them, untill one of these two things happens the world is out of ballence and there is no justice.
revenge you say?
so what?
revenge is an integral component of the human understanding of justice, it is just as universal, and many cultures fully embrace the concept. yes it is a deterant, and yes it is punishment, and yes (in the case of life in prison or death) it does remove dangerous people from society, these are all good rational reasons, nice and logical, but they are simply that rationaliseations for people unwilling to simply accept vengance and justice as good enough.
there is a reason why you feel like beating this person to death when you read about him. it's natural, it's the way humans are suposed to act, to force yourself to behave diferent is unatural, it goes against your nature.