It's not so much a lifestyle choice, so much as an opinion they're born with. They find members of the same sex attractive, same as straight people find the opposite sex attractive. If they wanna fuck or drool over members of the same gender as themselves, so be it, so long as they don't come hit on me. Live and let live, but yo bro, I don't swing that way.
Most people don't really understand homosexuals though, same as they don't understand a lot of things. The same degree of misunderstanding transfers to people of any uncommon lifestyle choice. Serial killers, users of hard drugs, pedophiles, shamans, nerds of any type, people of varying religious beliefs, and even sects of the same religion.
The closest groups I can associate with homophobes are probably racists, pro-lifers, and fanatics. In any case, they believe that their opinions and views are superior to others (as most people do about their own opinions) and that people shouldn't have a choice and need to come around to their way of thinking, when in fact an opinion is a difference that an individual or group of individuals are going to have.
I am no exception, I feel that my views are superior, but I feel that way because I believe that no one should hate someone else or discriminate against them just because they have different views. Again, live and let live. Let people be different, and value that difference, because shit would be boring as fuck if everyone agreed on everything, it'd be like a buncha damn clones. Fuck all that.
But I digress.
As for the whole "They can't help it" thing, that is true, they are generally born with a tendency to be attracted to members of their own gender, but it's often used in a manner that implies the individuals in question look down upon or pity homosexuals, which is kinda fucked up since there's really nothing wrong with them. Just because they're different than you doesn't mean there's something wrong with them, and though no one is perfect, homosexuality isn't an imperfection, merely a variation in taste.
That said, haters gonna hate and the unenlightened gonna be ignant, let em.
Just like homosexuality, there's no cure for stupidity or discrimination.