What I take issue with is this:
...the notion that some children might be the bad seeds of more or less decent parents — is hard to take.
It goes against the grain not just because it seems like such a grim and pessimistic judgment, but because it violates a prevailing social belief that people have a nearly limitless potential for change and self-improvement.
Does anyone really find it surprising that some people are just bad and that it's not the result of any outside influence? Isn't this idea central to the old nature vs. nurture debate no one bothers much with anymore? Did society move at some point to thinking absolutely everyone was capable of expressing bright and shiny goodness and I didn't notice?
I'm pretty sure society thinks the same as it always did, some people are plain rotten and it doesn't matter much why (except in how to reduce this in the future). It's not anyone's fault, just the way it is and always was. That's why we need nasty bad things like government, to help keep the nasty bad people in check. If it weren't for that, we'd all be living in a utopia of bright and shiny goodness with no need for anyone to tell all the bright and shiny good people what they should and shouldn't do.