I'm a little wary of posting this, as it really feels like a swiftboat type attack. The first source I read it on (and believe me, I have a vast variety of sources...) attributes it to a professor in San Fran, though discussion reveals it probably should be attributed to another source. I'm linking to it at snopes.com, with the intention that if it proves to be a fabrication, they will break it first, or at least rather quickly.

The author of this "letter" describes her week on Turtle Island with John McCain; and paints him to be an arrogant, racist, sexist bastard.

FTFA:

Needless to say I was irritated at his large ego and his rude behavior towards his wife and other women, but decided he must have some redeeming qualities as he had adopted a handicapped child from Bangladesh. I asked him about this one day, and his response was shocking: "Oh, that was Cindy's idea - I didn't have anything to do with it. She just went and adopted this thing without even asking me. You can't imagine how people stare when I wheel this ugly, black thing around in a shopping cart in Arizona .

It's ugly, but not much more of a stretch than calling his wife a cunt at a rally...

The rest of the "letter" at snopes here.