I think your description of them says a lot about your arguments nature.

I mean of course the parent are to blame, but since they too belong to what you describe as underclass they simply do not have the mental surplus.

If you have kids you will know how hard it can be to control their whereabouts.

And as far as I can se, no one is claiming it's an excuse. It's an explanation. You can then as you do choose to disregard it or you could perhaps try and look at the root cause and accept that social status and income do have an effect.

I think that poor parenting is to blame, partly. We can argue how much it is to blame another time. Sticking with parenting:

I don't think saying "[bad parenting] will always exist" is constructive or helpful. What's important is that there is less bad parenting over time.

So if it would be a good thing to have better parenting the question becomes what would have to be done for this to happen?

There were also some examples of good parenting - one chap handed himself in to police because his mother recognised him on television and forced him to give himself up.