donewithitalltodayandxmas - "Maybe each case should be looked at separately with no perceived views against either side"
Agree 100%. There are five instances in my family or involving close friends where the mother was, how should I put it, "psychologically fragile" (?) quite possibly due to known past trauma (in childhood or previous abusive relationships), in some cases involving alcohol and drug dependency. It was the fathers who provided stability and safety and, when some of the children were abandoned by their mothers, it was the fathers and grandparents who took over their care.
In all cases the mothers accused the fathers of "parental alienation", in one case citing it as one of the reasons for divorce (real reason was wanting to move abroad to marry her lover). None of the fathers did this, instead providing reassurance that the children were loved and never bad-mouthing their mothers.
In all cases, the fathers did their utmost to support the children in remaining with their mothers as primary carers whilst being vigilant about their safety, supporting them financially and going to court to get agreement that they would have frequent overnight stays - in order to ensure that the children were fed, washed, had clean clothes, were provided with necessary medication, etc.
I have just written then deleted a far too lengthy account of the physical and psychological abuse the children were subjected to by their mothers and the desperate measures some of them took trying to escape. Just one extreme example, where "escape" included attempted suicide. In that case the 14 yr old daughter ended up in a DV Refuge and would only disclose her location when she was assured that she could go to live with her father. (She did not know that her mother burnt all her clothes and belongings as soon as it was apparent she had gone missing, not knowing that her daughter had attempted suicide but in expectation that wherever she was that she would not be returning home.)
My own father was a text-book case of the "charming man" outside the home who beat and psychologically abused my mother, my brother and myself. I have no illusions about how bad some fathers can be as partners and parents and how well they can fool outsiders. Having been very close to both parents in the cases I have mentioned, I also have no illusions about how bad some mothers can be as partners and parents and how well they can fool outsiders too.
I am sure some fathers are guilty of false accusations of "parental alienation" by the mother but I am troubled that the emphasis in the OP is on the relationship between the parents. The priority has to be safeguarding the children. It does them a disservice, will cause more trauma and will put some of them in very real danger if we do not acknowledge that either or both parents can be guilty of abusing their children in this way.
Whether this abuse needs a special label is a different matter. If it results in very distinct damage to the child that can be differentiated from other psychological problems in the ICD or DSM, then maybe it does. If not, then it would seem hard to justify listing it separately.