The word homophobia, in spite of its etymological pedigree, broadly denotes any failure of total, evangelically supportive approval of what would classically be referred to as an unchaste lifestyle. In political or social discourse, use of the term tends to be most effective when the user genuinely (or, at any rate, convincingly) feels aggrieved or morally outraged because of some real or imagined slight. There is no requirement that the object of the homophobia epithet experience fear or anxiety in the presence of homosexuals or when exposed to homosexual behavior, however, fear or loathing in the proximity of homosexuals or homosexual behavior is generally understood to be proof positive of homophobia, regardless of the actual cause of the emotion in question. Invoking homosexual identity or lifestyle as a reason for discrimination under any circumstances is also generally regarded as proof positive of homophobia.
The author of this definition cheerfully acknowledges that he is homophobic according to the criteria given. If you, the reader, do not see yourself in that light, don't worry, you will, eventually, even if the definition has to stretch yet further to accomplish this miraculous feat.
See, also, Heterosexism.