I absolutely believe a parent can put a child in the position of thinking their other parent is bad.
I do not believe that the courts or social services are any good at all at finding the people who are genuinely doing this, and I think they throw around PA as a nuke button to end cases so they can close them, get a judgement, and move onto a less annoying aspect of their caseload that doesn't require as much critical thinking.
My own mother did her best to alienate me and DSis from my stepfather and father. She got full residency for my sister (the case took so long I was actually 18 by the time it got anywhere so I moved in with my father 400 miles away), and DSis ended up in care 6 months later when my mother lost her rag and I wasn't there to protect her that time. The courts and social services let this happen, believed my mother completely when she accused my stepfather of DV and SA, and they couldn't spot what was really happening from a mile off even though DSis and I actually told them everything two years earlier; we were not believed. I do not trust them to make good decisions.
People who believe one party is "all good/right/worthy of having the children" and one party is "all bad/wrong/unworthy of having the children" and who believe their job is to identify which is which have no place doing the jobs in the family courts or social services. No human being is absolutely infallible and if you dig for long enough you'll find flaws in even Jesus.
Unfortunately, a lot of them seem to subscribe to the viewpoint that they need to decide whether mum/dad is good/evil, and they seem to make those decisions based on their own projections, unresolved traumas, and whatever feels they get from the short amount of time they spend face to face with the people involved instead of following the actual evidence and interpreting it correctly.
My mother, like others with certain personality disorders, was an expert at reeling people in and getting them on-side even though the evidence didn't even slightly match what she was saying.