Homophobia is a term commonly used when gay bashing breaks out like disease. It's not a difficult term to grasp.
Consider three attractive men standing across from three attractive women. Suddenly two of the men become amorous with each other. Does the third suddenly attack them. If he was homophobic he would. His interest in homosexual men would supercede his interest in heterosexual women. If he were a heterosexual man, however, he would naturally ignore the homosexual men or even encourage them, all the while gleefully delighted he now had three women for himself.