There's also the normalization of seeing and hearing awful things. After a while of being exposed to the wretches of humanity you begin to see the signals for the wretches everywhere.
As the warrior poet Maslow put it, "if the only tool you ever have is a hammer, you tend to see every problem as a nail."
I actually strongly suspect that this is a major issue with cops. Even the most well-meaning new hire is likely to become jaded and paranoid after years of interacting primarily with criminals. They are probably more likely to assume the worst of a given stranger, even in contexts where there is no reason to suspect that stranger.
Totally, child abuse pediatricians, forensic pediatric pathologists etc. are exposed on a daily basis to the very worse things imaginable in the world (autopsies of babies beaten to death and so on), and yet they need to keep a calm and rational stance by analyzing facts objectively. This is hard and they don't always succeed. Some are led to see the worse in everyone and they see potential child abusers in every parent and caregiver.
This can go quite far, with some experts stating that the histories reported by parents and caregivers bringing a child to the hospital with some injuries are always falsified. This can surely happen, but a foundational tenet of medicine is to listen to the patient/parents.
I've seen experts concluding to abuse in 100% of their cases, including those where children hah obvious, DNA-proven genetic conditions causing the observed injuries. Fortunately, some judges remain reasonable and act as "gatekeepers" by exculpating parents and caregivers despite affirmative opinions by reputable experts. But many don't.
As the warrior poet Maslow put it, "if the only tool you ever have is a hammer, you tend to see every problem as a nail."