Details of the rapper's letter emerge after Abdirahiim Hassan is jailed at Derby Crown Court.
The rapper's representatives say the series is "a shameful hit piece" that "relied on stolen footage".
Headlining the festival's eighth instalment are 50 Cent, Biffy Clyro and Snow Patrol.
Charli XCX and 50 Cent headline Manchester's biggest music festival at Heaton Park this weekend.
The full-line up for Parklife 2025 is unveiled with the American rapper to headline.
One tattoo featured the words Get Rich or Die Tryin', which is the title of 50 Cent's debut album.
The three-day event, now in its eighth year, takes place on Glasgow Green from 11-13 July.
The award-winning hip-hop producer was presented with a star on the Hollywood Walk of Fame on Tuesday.
