It's more about personal freedom. Mann, a self-described compilation filmmaker, argues that his seemingly flippant treatment of a serious subject helps dispel decades of reefer madness. Look at Mad magazine. Mad really influenced the counterculture. It showed us how to use humor in making a political point.
People go see the movie because it's funny.
Humor helps get the tragedy across. I think that's good. I'm making a movie . I want to make it entertaining . As in his earlier films, Comic Book Confidential and Poetry in Motion , Grass is Mann's heartfelt attempt to serve and protect sides of American life that often get snubbed by mainstream media.