In David Henry Hwang's play M. Butterfly, Gallimard is a metaphor for Orientalism because he views Song as the idealized, mysterious "Other." In Edward Said's explanation of Orientalism, the "Other" is placed in a position of hierarchical subornination, and this is what Gallimard, from his perspective, has done to Song. Readers understand that Song has actually tricked Gallimard into this position and actually has the upper hand; however, for Gallimard to admit this he would also have to denounce his sense of manhood that he has constructed around his relationship with Song. In the dichotomy set up by Orientalism, the West is strong, because the East is weak: in Gallimard and Song's relationship, he is strong because she is submissive. Admitting that the relationship was never valid is the equivalent of saying that Gallimard's sense of manhood is also invalid.
On another note, there is a line in the play that says that the perfect woman can only be created by a man. Ironically, this is what happens when Song takes on the persona of a woman, so Gallimard, for 24 years, had "the perfect woman."