Nobody is making that strawman of an argument. Most states give CPS very little (or no) ability to simply ignore reported child abuse. They get reports and they have to investigate.
"The local law enforcement agency is required to investigate all reports. Cases may also be investigated by Child Welfare Services when allegations involve abuse or neglect within families." [0]
Just one example, but 27 states came up in my search for where CPS has little or no latitude in choosing which allegations to investigate.
That is precisely what was happening in the examples the original commenter provided [1]. Why are you compilating CPS being legally required to investigate a report and the CPS targeting parents?
[1] they almost all exclusively believe they were being unfairly targeted for past transgressions or unfair accusations.
"The local law enforcement agency is required to investigate all reports. Cases may also be investigated by Child Welfare Services when allegations involve abuse or neglect within families." [0]
Just one example, but 27 states came up in my search for where CPS has little or no latitude in choosing which allegations to investigate.
[0] https://www.cde.ca.gov/ls/ss/ap/childabusereportingguide.asp