You haven't known those people for their whole lives. You haven't seen them at their very worst, in the moments where they did the things that haunt them for d

You haven't known those people for their whole lives. You haven't seen them at their very worst, in the moments where they did the things that haunt them for decades. That's the point here - some people do less nasty stuff than others, but all of us have treated others horribly at some point. "Pieces of shit" may not be the best phrasing. I'd say "When you meet a person, no matter what they seem like, you can be highly confident that they have done something wonderful for someone at some point, and that they have mistreated someone horribly at some point."