My argument is one based on deterrence, and yet few people counter that and those that do simply respond with something along the lines of "well acktually, people only start caring about consequences when they are a legal adult, minors are incapable of understanding the threat of having their lives destroyed before they can even get a chance to experience them so we should just ignore all the evil acts they commit".
It's that same overly lenient attitude towards minors which make them think they can get away with things, if punishments are harsh, regular, and criteria to be declared guilty is loose then they will be too intimidated to do anything they view as potentially disagreeable. As a kid I was disproportionately punished by everyone, often for simply being the victim or even for things that had never happened and it made me a better man in the end because I was and still am too afraid to do much of anything that I'm not directly told to do and not to express any views when dealing with people who have any sort of connections to me. The world would be better off with more people like me.