[Ren isn't certain if this question will go anywhere productive—he's used to being judged—but it's a potential taker. He's not ashamed of his motives, either.]

To prevent those who would abuse their power from harming others.

[That's a very noble goal for a known violent killer. ... But he's actually being a hundred percent sincere here, even if the "others" he's mainly concerned about are the people closest to him.]

The law enforcement here is limited in their effectiveness, and those strong enough to stop others may not always be available or care enough to do so.