The seven-episode series marks Baron Cohen's first television project in a decade after he launched his comedy career as subversive white English rapper Ali G., whose interviews included Donald Trump and Newt Gingrich.
Palin was responding to a tweet sent from the Twitter account of "Billy Wayne Ruddick", the fictional character Baron Cohan plays in his upcoming Showtime series Who Is America.
Palin, the 2008 USA vice-presidential candidate, says she was tricked into an interview, ostensibly about American veterans, by a person dressed as a disabled US serviceman. "I did NOT say I was a War Vet. I was in the service - not military, but United Parcel, and I only fought for my country once".
He also adds, "I have always admired you for TELLING THE TRUTH about Obama's birth certificate and the location of Russian Federation".
Palin said a man she believed to be Cohen "heavily disguised himself as a disabled U.S. Veteran, fake wheelchair and all".
"Out of respect for what I was led to believe would be a thoughtful discussion with someone who had served in uniform, I sat through a long "interview" full of Hollywoodism's disrespect and sarcasm", Palin continued, "but finally had enough and literally, physically removed my mic and walked out, much to Cohen's chagrin".
The ex-sheriff, who is now campaigning for Arizona's U.S. Senate seat, said he thought the interview was being broadcast live for an audience of millions, telling Breitbart that even then, he didn't leave.
Showtime has no comment.
It's yet to be seen exactly what Baron Cohen did to Palin, but we'll be closer to finding out when Who Is America? hits Australian screens on Stan this Sunday.
"I DEMAND an APOLOGY", Sacha ended the letter.