This might not be much of a diary (and if it isn't... meh), but today is the 5 year anniversary of the publication of the Gettysburg Address of Hate Mail known by it's opening of "Dear Socialist Fuckstick"
I don't know if it gets better or worse with time, but as far as I know, it's still one of the most memorable. It's a wee bit dated now (does Bill Ayers still make the talking points these days?), but it still features some content that's timeless, like Russia no longer existing, or failing to understand scientific method and science in general, or the attempts to sound intelligent with complex words. It had almost everything one would expect in a piece of hate mail.
Real or fake, it's still a classic that set new standards for hate mail, both here on the Daily Kos and elsewhere.