From what I see, a fixed number of people will be subject to the predatory behavior of the underclass. We are collectively unwilling to fix this. I don't see a compelling reason why it matters
which children are victimized this way.
Now if you want to say that none should be, I agree. Find a way to stop crime. Spreading crime around is not that way.
(FYI my thinking on this issue draws far more from neo reactionaries than libertarians.)