The MPAA's Classification and Rating Administration assigned the rating because of repeated use of the F-word.
"The language in the film is a reflection of reality in our schools, on our buses and online — something these kids experience every single day. It’s not sensationalized 'adult content,' as your rating suggests, and is oftentimes an active part of bullying itself," Honda wrote.
He said the MPAA should not try to "censor reality" and argued the educational benefits of the documentary outweigh its use of profanity.
Twenty lawmakers, including Democratic Reps. Raul Grijalva (Ariz.), Jared Polis (Colo.), Jackie Speier (Calif.), Jesse Jackson Jr. (Ill.), Joe Baca (Calif.), Barbara Lee (Calif.) and Dennis Kucinich (Ohio), have signed Honda's letter so far.
In his letter, Honda notes that a Change.org petition from Michigan high school junior Katy Butler urging the MPAA to re-rate "Bully" PG-13 has attracted nearly 270,000 signatures.
The movie's studio, the Weinstein Co., appealed the MPAA's R rating. The organization's appeals board voted 7-6 to overturn the rating, but a two-thirds vote is needed.
“The voluntary ratings system enables parents to make an informed decision about what content they allow their children to see in movies," said Joan Graves, chairwoman of the MPAA's ratings administration. "The R rating and description of 'some language' for 'Bully' does not mean that children cannot see the film. As with any movie, parents will decide if they want their children to see 'Bully.' "
She emphasized that the rating is not a judgment on the value of the movie.
MPAA spokesman Howard Gantmann said the organization could change the film's rating if the studio releases an edited version, but otherwise, the "rules are very clear."
"Bully" will open in New York and Los Angeles on March 30 and in other cities on April 13.
Dodd will participate in a panel discussion with producer Harvey Weinstein and director Lee Hirsch after a screening of the film in Washington on Thursday. The organization invited Washington-area teachers and principals to view the film and participate in the discussion.