There is definitely a good argument there. A child has far more potential years of life left than an elderly person, so killing them seems worse. Perhaps that

There is definitely a good argument there. A child has far more potential years of life left than an elderly person, so killing them seems worse. Perhaps that's one reason why we tend to think so badly of child murderers. Of course, in reality (at least the American judicial system), punishment is usually based more on other factors, such as motive. So premeditatedly killing an old man because you wanted to steal his stuff is punished more than killing a child purely by accident.