ETA: this post was pretty much refuted by comments below.
I've noticed a situation several times that I think deserves attention.
Somebody goes around saying they've been the victim of mistreatment. But they seem mentally ill. Whether or not you know of a diagnosis, they seem "off" somehow -- highly agitated, making social faux pas, telling stories that don't quite add up. So people are very suspicious about whether their allegations are true.
Is this rational?
In general, someone who seems less trustworthy should be believed less. And, yes, mentally ill people are more likely to be delusional or exaggerating. But they are also more likely to actually be victims of crimes than the general population.
40% of women in the UK with severe mental illness are victims of rape or attempted rape.
People with severe mental illness are 6x as likely as the general population to have recently experienced sexual violence.
30% of mentally ill adults in an American study had been victims of violent crime in the previous six months.
Mentally ill adults in Sweden are 5x more likely than the general population to be murdered.
More than 25% of severely mentally ill Americans have been the victims of a violent crime in the last year, 4x the rate of the general population.
30-33% of psychiatric patients have been victims of domestic violence.
Someone being mentally ill is evidence for, not against, their being victims of a crime. And the base rates of violent crime are pretty high, so all things being equal, "someone attacked me" is not an extraordinary claim. Even when someone seems crazy and has made a lot of claims you don't believe, it can be reasonable to believe their claims of crime victimization. Don't fall into the horns effect.