If you have a phobia you possess an irrational fear. A homophobic person, this implicitly suggests, therefore holds an irrational fear of gay people. Or, often, hatred. Indeed, there are such people in the world. My problem with the term is that it has come to be applied to anyone who disagrees, however rationally and calmly, with the political or social goals of homosexual people.
A priest reads scripture and concludes that he can't perform a gay marriage is a homophobe.
A conservative politician votes down a bill letting lesbians adopt children, citing the importance of the traditional family model in the raising of a child. He is a homophobe.
These are hypotheticals. The views aren't necessarily something you'd personally support, but they are based on reason (or at least something unrelated to whether same-sex people gratify one another) and not irrational fear. I feel that 'homophobe' has simply come to be seen as a word which can shut up people who disagree with or refuse to implement a wide range of political, religious and social values which LGBT folks believe are central. These people don't hate gay people or try to stop them from being gay. They simply disagree with them.
To use a personal example, I'm of the strong opinion that priests/ministers/churches/whatever should be able to refuse individuals marriage if they want to, especially when their faith holds that they should. This includes gay people. Am I therefore a homophobe, frothing and dangerous? Who knows.
Something loosely similar is happening with the word 'racist'. For instance, Meghan Markle. Britain has been labeled racist for not welcoming her. The irrational fear here is against black people. Because she is black, it must be racism.
In reality I've never heard or seen anything remotely racist directed towards her, even in casual conversations, never mind the media. But she's a black woman who broke up the royal family and is currently leading the nation's darling, Prince Harry, around by the nose.
Is the nation racist, or does it simply not agree with Meghan's ambitions?