Peterson is basically talking about helplessness here. Being an innocent, nonconfrontational person might seem good in a lot of ways, but Peterson suggests that overly trusting, submissive behavior actually enables other people’s bad behavior. Peterson suggests a rather surprising thing to counteract it—realizing one’s own capacity to inflict harm, even if it's only theoretical. Basically, it’s difficult to resist evil if you don’t have at least a theoretical understanding of it and the reality that, on some level, most human beings can inflict it, or at least are tempted to.