Empress Rou, it was a similar situation that inspired this post. It's been my experience (from one that happened to me, and from hearing what others have had to say about their own experiences) that it is some of the carefully cultivated Sweet Kind Personae (i.e., who make it a point to mention how sweet & kind they are, or sensitive, or whatever) who send the angriest, nastiest PMs. Just like what you describe.
I wholeheartedly agree with the rule that says you cannot post PMs on here, but I would love to see the expressions on the faces of the people who are fans/supporters of the SKP (who usually garner a few because they are also likely to cry foul over a number of issues) if the admirers could see some of the seething content written by the SKP.
SK probably stands for "sincerely krazy."
: If you are a genuinely sweet kind person, this does not apply to you.