"Homophobia" is not a very felicitous term, in that it suggests that the cause of "homophobia" lies within the mind of an individual, in separation from social relations. For the same reason, those who denigrate "homosexuality" as a kind of mental disorder or a defect of nature commit the same error of attribution.
In contrast, the term heterosexism, while it is rather ponderous, has a virtue of implying an (historically created) ensemble of _social relations_ that create oppressions of those called "homosexual" & "bisexuals."
The feelings often described as "homophobic" are complex & cannot be reduced to the dislike of "their ["homosexuals'" actual or imaginary] habits." The feelings seem to be a mixture of the following:
1. Fear of appearing "homosexual." 2. Fear of oneself becoming (or turning out to be) "homosexual." 3. Fear of being victimized by the "homosexual."
1 is quite obvious, in that much of "homophobic" behaviors originates in the desire not to appear "homosexual" -- the desire obviously caused by the fact that, in this society, to be or to appear "homo" carries penalties ranging from mild disapproval to lynching. Since one does not wear one's sexual preferences (actual or imaginary) on one's sleeve, it seems to some (especially some young men) that they need to "prove" their "normalcy" by creating & oppressing the "abnormals." Because it is impossible to "prove" one's sexuality once and for all, "homophobic" behaviors tend to assume a character of compulsive repetition that does not achieve its end (= proof of "normalcy").
2 is less obvious, so allow me to quote the late and lamented Quentin Crisp to illustrate my point: "Mainstream people dislike homosexuality because they can't help concentrating on what homosexual men do to one another. And when you contemplate what people do, you think of yourself doing it....That's the famous joke: I don't like peas, and I'm glad I don't like them, because if I liked them, I would eat them, and I would hate them" (_The Celluloid Closet_, dir. Robert Epstein & Jeffrey Friedman [based upon the work of film historian _The Celluloid Closet: Homosexuality in the Movies_], 1995).
As for 3, it is a common ideological inversion of victims & victimizers. The oppressed appear as "victimizers" in the eyes of the oppressors. Gay bashers used to make use of the "homosexual panic" defense regularly; and the "homosexual panic" defense used to allow them to avoid legal sanctions against violence frequently. This defense is still being invoked by the gay bashers today, but nowadays the judges and/or the juries do not necessarily accept it. This may be properly called progress.
Yoshie