Not only does Gallimard never suspect that Song is man, he does not even want to believe the truth after Song's true identity is revealed. No one of course believes this because it seems absurd to carry on an intimate, long term relationship without knowing the sex of one's partner. However, Gallimard maintains that he did not suspect that Song was a man. Gallimard is totally wrapped up in his fantasy of the perfect woman, and this fantasy pervades his relationship with Song. Keep in mind also that Song goes to great lengths to conceal his true identity from Gallimard, and Song uses Gallimard's desire to believe in the perfect woman to his advantage in the concealment. I do not think that Gallimard is gay--he loves Song as the ideal woman because she embodies all the stereotypes that suggest he is superior in his masculinity. His being gay would not support this. Rather, as Song says, the perfect woman could only be created by a man, so Song creates Butterfly to appeal to Gallimard's weaknesses.