When it comes down to it, a lot of Homophobia comes from: Lack of knowledge, and Immaturity.
As a Heterosexual, with a dozen or so Homosexual friends - I honestly couldn't care less.
We're both human, we're both compassionate, and other than who we find attractive, there are little to no differences between us, other than personality traits which everyone differs in.
The immaturity element comes from school. To a certain extent it's very apparent in gaming too. How many people have you heard use the word 'gay' to describe something as bad or odd? I know I've heard it - many, many times. However, it's something that has socially happened.
Young kids as young as twelve use it, and I'm not even sure they actually know what being 'gay' actually means. It stays with them though, until their teenage years, and into their twenties. As soon as they meet a Homosexual, suddenly there's fear and uncomfortable feelings. Like they've just met a mythical creature. All this negativity towards a word, when they finally meet someone who is just that - they don't know how to react.
Unfortunately when people are backed into a corner, or in an awkward position, many lash out - and that's where the hostility, and aggression comes from.
These people are generally the same people who say truly stupid things like: 'Get that queer away from me, he might try raping me.' Seriously? Are you really so arrogant you assume you are irresistable to Homosexuals? I might find a woman attractive, but it doesn't mean I'm going to jump on her. Women may find a guy attractive, are they going to jump him? Probably not. There are exceptions to the rule, but that's mankind for you.
As others have said, many of those that are terribly hostile towards the gay community, may have repressed feelings themselves. To distance themselves from such people, may make them feel more comfortable, as they are terrifed of 'coming out' and what consequences that may have on them. It's a shame that people feel this way. They aren't helping the problem though, they're actually making it worse. Hatred spews hatred. The problem gets worse, meaning that when this individual does 'come out' the consequences they face could, possibly be more severe than before.
I've heard the argument many times, that being Homosexual isn't 'natural.'
Fair enough, two men can not conceive a child. However, I'd put it to all of you who think that way: How many unnatural things do we as humans do?
How many of those that think this way, jump into a plane and fly? Is flying natural?
Jumping into a car to travel of speeds up to around 120 MPH, is that natural?
Is contraception natural?
I really could go on, but you get my point - we live in an evolving world, little of what we do now 50 years ago was natural. Would a black president have been elected 50 years ago? I highly doubt it.
As a society instead of shunning or putting up barriers between Heterosexuals and Homosexuals, there needs to be discussion. Get people to understand those they may fear. Once the fear is gone - so should the hatred/abuse.