[It sure does sound like he's quoting someone.]

Whoever said that to you wasn't incorrect. But I will state it again: there's a marked difference between killing someone for your own selfish reasons, and seeing someone punished for their misdeeds. I am a detective, Dio, my work has condemned criminals to death before. But doing so is to prevent them from continuing to harm innocents...including now. If we allowed you to walk free, you would have killed all of us simply to escape.