How can i convince my parents to let me watch R rated movies that have .?

Look im just wondering because i wanted to see harold and kumar escape from guantanamo bay, it has some graphic . Im not perverted. Im 13, and i appreciate good movies ( like michael clayton, lucky number slevin, saving private ryan...). I just want to be able to watch a new variety of movies. Im allowed to watch anything rated R as long as it doesn't have . Just trying to help your answers.