I think the word came into to use because of early claims that fear that one might be homosexual is a common factor among those who most oppose homosexuality and the name stuck.
There was a study done about 30 years ago. They took 3 groups of 50 men: 1 group was homosexual, the 2nd group was heterosexual, but said they weren't really bothered by homosexuality, it just didn't have any appeal to them, the 3rd group were heterosexual men who said the hated homosexuality.
Each group had their genitals wired to a sensor and were shown a gay pornographic movie.
As expected - 100% of the homosexual group experienced erections. 8% of the heterosexuals who didn't care about homosexuality experienced erections. 80% of the heterosexuals who "hated fags" experienced erections.
The term "homophobe" means exactly what it says - people who are "scared" of homosexuality - not people who don't "like" homosexuality. There's a big difference - and the study proved it. If you truly "hate fags" with an intense passion - there might be a reason.
I happen to not care for asparagus - so what? I don't even want to watch someone else eat it - so what? However, if it became an over-riding passion of my life - to actively hate asparagus and asparagus eaters, then I would have a problem.
The upshot is: sex is no different than eating, they are both bodily functions and they are both a matter of taste. If I don't care if you like Chinese food or not - why on earth would I care about your sexual tastes? Unless I plan on seducing someone - I couldn't care less about their personal sex life. Why would you?