I think building a policy based on the possible existence of a vanishingly small group of bad actors is a great way to make excuses for avoiding solving real problems...
I'm not saying that it's right to lump people together like that and BPDs in particular don't take well talking shit about them.
However, some people with mental issues in some situations really pull off lies and deception which blow most people's minds. I've been in situations where people in charge wouldn't believe some things happening right under their nose because those things were simply too bold and, well, insane. And because people are easily manipulated into forming good opinions about others and apparently don't like learning they have been wrong.
You're conflating two different things: if 1.6% of the population has BPD that still doesn't tell you that 100% of them are untreated and spending their time and credibility making false accusations, or that those wouldn't fall apart fairly quickly. That might happen on TV but most real people with mental illnesses spend time trying to minimize their impact on others, not act like the bad guy in a police procedural.
