Our category of identity traps us into its mold and this mold helps to shape our thoughts and behaviors.  In this case, it is very much the person’s identification of himself as heterosexual and his belief about what heterosexuality is and isn’t that is causing his fear and anger.  If, for example, he were to have thought of heterosexuality and homosexuality as categories of actions and not of people, and thus didn’t rigidly designate his own sexuality and bound his thoughts and behavior by it, then he would not have been afraid of what the possible interest in other men meant and he wouldn’t have reacted with anger.

So, perhaps we should say that homophobia at the end of the day is a fear of being the same as something that you find repugnant. And the more you try to push it away in yourself, the more militant you will be about it in others.