Through my work I interact with NY offices of child welfare, and holy shit, they are constantly terrified to the point of psychosis about backlash from the public. ACS has had some pretty high profile abuse scandals in the last decade. As you point out, all or most of those cases are abusive parents who already have an (overworked and underpaid) social worker. It’s so bizarre that it translates into this stranger danger bullshit.
Men definitely dominate the world of internet driving trollies in both viciousness and volume, BUT if you ever do want to see female internet trollies on full display, visit a parenting forum. I guarantee you will be threatened with a CPS call within minutes from both sides of the issue.