Very recursive. So when he sees a person killing someone, before he decides whether to take action he requests a complete police file on the dead guy to see whether or not they deserved DEATH! themselves?
Anyway! Back on something vaguely approximating on-topic (interesting thought: whether something is on-topic or not is a subjective question ... no! bad Fice!)
His way of thinking is very simple: He believes, that he is good and that there are many evil people in this world. So he decided that if he killed the evil people, there would not be evil anymore.
Funnily enough I was watching Gundam 00 the other day (a series I firmly believe has a truly awesome concept and story which was then kneecapped by a production team intent on making Generic Mecha Series #638) and that's pretty much the concept there. Of all the many, many factions that end up having a right old shindig, there's only one you could describe as truly evil, and that's the traditional Insane Nutter Antagonist. The 'evil empire' has many minions who firmly believe uniting everyone into a single nation is in humanities best interests, the protagonists are ostensibly against anyone starting a war regardless of whether it was justified retaliation or not (their preferred method for dealing with armed conflicts is shooting anyone who has a weapon regardless of who they are, which is one reason I prefer them to the normal wishy-washy protagonists we usually get), the third faction who gets involved claim to have the same objectives as the protagonists, except we're
better at that than you are, so you need to be stopped, etc, etc.
I really quite enjoyed it, mainly because everybody who got involved was guilty of being horribly biased and imperfect, which seemed sort of realistic to me compared to the normal mecha whitewash.