74, Stanley Milgram’s experiment shows that 60-66% of “nice” people can do heinous acts if an authority figure tells them to do so… So, my black market milk producer could become violence under a stressful situation or sell me out to the authorities and let them violate me. We cannot predict who will sell us out. If we think we are wise enough to see into people’s hearts during times of stress, we might to our horror, learn how wrong we can be.
As for the evil character in your story, people like that usually give lots of warning. I stay well away from people like that.