I was just watching one of those Tanya Byron shows, and a young mother absolutely exemplified that thing about judgement. Early in the show (before much interaction with Tanya) this young woman brought me to tears the way she interacted with her daughter. They were playing, being playful with some crisps, and the 18 month old dropped one on the ground. She picked it up and ate it, grinning and laughing with her mum. Mum then called her a "scrag", scowled and turned away. The child looked like her whole world had crumbled. It was nothing short of awful.
Later, the back story becomes apparent and the situation rapidly improves. The only difference between this Bad Parent and the Earth Mother guiding her brood through tranquil gardens is circumstance and understanding (and in this case 5 days or so of intense training and therapy).
Strangely enough, she loves her kids and wants them to grow up happy and healthy just like everyone else. I'm guessing the mum in the supermarket was probably the same.
I should also mention that while this was a lone female parent, whenever there is both parents present, both are regarded as equally critical in raising kids. Tanya permits no patriarchal buck passing by dads.