I think that what most people are saying is that in many cases these parents aren’t any more negligent than the average parent–it’s just that their mild negligence happened in a time and place where it had horrific consequences.
By analogy: lots and lots of people drive drunk all the time and never get caught, certainly never hurt people. Some drunk drivers manage to kill people. Obviously, the law can only punish the ones that it catches, but on a moral level, is the drunk driver who kills someone really more evil than the one that doesn’t? Or are they both equally evil, and some just get lucky and their evil decisions never lead to a bad outcome?
I’ve never left my kid in the car. But I’ve done stupid things. I forgot to buckle the top buckle on his car seat, once. Could have killed him. I’ve forgotten that I had water boiling on the back burner, and left him in the living room within easy reach of it while I went to the bathroom. Could have killed him. Just typing those two things makes me queasy. Given that, the take-away I have when I read these stories is not “Oh, those stupid parents”, but “Jesus Christ, thank god that’s not me. I have to be CAREFUL. I have to be EVEN MORE CAREFUL. Jesus Christ. I’ve been so lucky”. I agree that those parents are negligent. But by that standard, so am I. I’m a terrible fucking person, because I am not perfect, and my son needs perfect, deserves perfect, must have perfect. And that’s why your condemnation hits so hard–because it’s condemning me, too.