Kevin T. Keith at Sufficient Scruples examines how fathers' rights organisations attract pseudoscientists making up mental illnesses that their harpy ex-wives must be suffering from that both explain why they're being difficult about visiting rights and why the courts should just take those kids away from the bitches:
Kevin describes it as:
"the right wing's penchant for dressing up their particular aversions in pseudo-medical language and imputing some sort of bogus pathology to people who have simply refused to behave as they were told."
Such pathologising has always been a pernicious problem for women with minds of their own though. Just think of the origins of the word hysteria. As Kevin notes at the end of his article:
"After all this, all that remains to be said is to note how pervasive the medicalization (specifically, the psychological pathologizing) of women's behavior is, predictably, in ways systematically tending to establish them to be unfit to live their own lives and raise their own children."
So, some women simply refuse to do what their ex-husbands want them to do in relation to child custody and access. That does not, however, make them mentally ill for jerking their exes around. It does not even necessarily make them arseholes out to "get" their exes. They may in fact have perfectly logical reasons to restrict access, no matter how much the ex-husband doesn't want to acknowledge that.
Do some women use their children as tokens in a punishment game with their ex-husbands? Yes, they do, and they are unethical to do so, even if their ex treated them appallingly during their marriage and the temptation to deliver retribution in the only way they can is overwhelming. It is still wrong to use the children in that way, and the older the children grow the more likely they are to resent it, so it's also counterproductive.
However, that doesn't, on its own, make them a bad custodial parent: just a difficult co-parent. Yes, that makes it hard for the non-custodial fathers, in many cases much harder than it should be. Acknowledge that she hates you and won't make life easy, resent it some, but deal. It's a cop out to say she's nuts, guys.