Though, if it's a child's dream...then people looking for world peace may also be living in a child's dream. If it is in the nature of humans to fight with one another, then the people seeking world peace are also seeking to change the "psyche" of humans, because true world peace is just not possible
For some soldiers, even for the sake of duty...does that free them of the fact that they will and have killed people. If it's duty, if it's wrong, they can still refuse to do it. If the know that it's wrong, and still obey that duty and kill...then they have crossed the line. If it's for duty, one might say that Light feels that it's his duty to do what he's trying to do for the sake of good people (like a soldier might feel like it's his/her duty to do it for his/her country).
That said, Light having power does give him an undeniable advantage over other people. And he does, arguably, have the power to change the world to his liking. And with that comes responsibility in seeing that world succeed that most people wouldn't want or have. He may not be "God", but he is a person with a lot of influence and power on how the world may turn out.
Light's plan to get rid of criminals for the ideal world is flawed, but then again, who can really claim an idea is really flawless? If humans aren't perfect, how can an imperfect human come with a perfect idea? If we wait for an idea to be perfect, nothing will be done. Light just took the initiative.
And yeah, I guess it's interesting. Otherwise, I wouldn't be writing all this.
