Nathan Heflick writes in Psychology Today:
Even a man who thought that women all want to have sex with their fathers and spend much of their life distraught because they lack a penis is right sometimes. This person, the legend that is Sigmund Freud, theorized that people often have the most hateful and negative attitudes towards things they secretly crave, but feel that they shouldn’t have.
If Freud is right, then perhaps men who are the most opposed to male homosexuality have particularly strong homosexual urges for other men.
One study asked heterosexal men their attitudes toward male homosexuality. Based on these scores, they then divided these men into two groups: men that are homophobic, and men who are not. These men were then shown three, four minute videos. One video depicted straight sex, one depicted lesbian sex and one depicted gay male sex. While this was happening, a device was attached to the male participant’s penises. This device has been found to be triggered by sexual arousal, but not other types of arousal.