[indigochill]

There is another aspect here which I suspect contributes the majority of the demonizing in this situation: being a single parent is assumed to be a sign of a broken relationship, which signals potential personal problems (whether poor judgment in a partner, poor conflict management, whatever). Of course, in reality there could be a plethora of other reasons, but this seems to be the assumed narrative.

On the other hand, consider the woman who's still single with no kids, maybe living at home with her parents, with no job. I suspect there'd be a lot less demonizing. Maybe even less so than towards the men, who are "supposed to be providing for a family".