A lot of people who are homophobic are actually gay them self, or perhaps bisexual with some homosexual preferences, or they are in very strict groups who hate homosexuals. In those cases, they act homophobic to try to fit in with the 'normal' group because subconsciously they fear of being outcasted. Even if they are not gay they might feel pressure to conform with the group's hate, otherwise might be labeled gay or a gay supporter. Then it is even worse if you fear that label might be real.