In short, if what they are writing is messing with your head/heart/causing your to doubt yourself, you've given them too much rope to tug at.
You're probably right...but I do learn after the first few times or so, I just have a hard time getting past that initial disbelief

A good example is Mary Mcgrannahan's most recent blog post where she accuses me of "hacking" SHE posted the log-in and password for the "Keep and Share" account where SHE posted the Subpoena to Sandra, and then SHE invited everyone to go look at it, so I did, and made of SCREENSHOT of what I saw ....and she calls that "Hacking" I've already posted a screenshot of the blog page where she posted the login and password
http://cassiopaea.org/forum/index.php?topic=8379.msg261953#msg261953...so I won't let myself get distracted by Mcgrannahan's latest lie...I'll keep working on Camwell's new expo-site.
I think a big part of the disbelief is that I get tons of "My ex {spouse, boss, partner, etc} is a psychopath" type requests for help each year, and in the vast majority of cases, the ex whatever isn't a "psychopath" at all, they're just an ordinary person who's angry, got a bruised ego, etc.
Once I start digging I can see where each party to the dispute has misunderstood or twisted something, or expected something they didn't get...stuff like that. No psychos, just stupid people tricks 101. Usually I mine all the data and give the FACTS to these people, and they're like "Ohhhh, well I thought" yadada yadada Then I toss them to a GOOD quality professional mediator to settle whatever's left of their dispute (usually property rights, occasionally child custody) and while both parties might still be a bit snarky, for the most part, they get it settled and over it.
REAL psychos like Barbara Camwell and Mary Mcgranahan are a LOT more rare than you'd think looking at the shape of our world.