Below: a handwritten plea, from Bob Dylan.
Transcript follows. Image courtesy of historian Jon Wiener, author of the utterly fascinating book, Gimme Some Truth: The John Lennon FBI Files.

Image: Jon Wiener
Transcript
JUSTICE for John & Yoko!
John and Yoko add a great voice and drive to this country's so called ART INSTITUTION / They inspire and transcend and stimulate and by doing so, only can help others to see pure light and in doing that, put an end to this mild dull taste of petty commercialism which is being passed off as Artist Art by the overpowering mass-media. Hurray for John & Yoko. Let them stay and live here and breathe. The country's got plenty of room and space. Let John and Yoko stay!
Bob Dylan