I never claimed they were at all logical. Conservatives? Nope.
To actually answer your question, though, it's a vicious cycle passed down from generation to generation. A bit of teasing others for being different is normal in children because of the fear of others, but responsible adults and parents teach children that that's not OK and a lot of people learn to share and be kind. Not so much conservatives. Conservatism is a developmental/learning disorder.
The ones that go on as adults to be loud homophobes and start making all kinds of claims about how it's a choice and objecting to the existence of gay literature or gay porn or out gay people are clearly still frightened, but of what? Why do they feel the need to make it so clear they want nothing to do with it? Why do they call gay porn temptation if it isn't tempting? Why do they worry that young people will see something gay and feel the urge to join "the gay lifestyle" if it left them cold and unmoved? Why so they call it a lifestyle choice if they never had to choose? The answer is really simple but somehow you can't see it and you instead deny it strongly.