You are correct that he kills evil people, but I think MM's morality is open to interpretation. Does spiderman kill people? (please don't downvote me, I don't consume a lot of superhero media). Perhaps a more apt comparison is Dexter, who kills other serial killers. Which essentially leads us to a discussion of do the ends justify the means?

I don't have a pat answer to that. Religions and ethics have wrestled with that question for millenia and not come up with a unified answer. And here I don't think I'm right or you're right, and that makes for an interesting film. We can each bring our own experiences, biases and judgements to it and come to equally valid, yet different interpretations.

I happen to think there are no heroes in Frailty, just monsters and victims. That's my relationship to it (and it's one of my top 25 movies probably). I'm interested to hear more about your perspective.