I don't even buy into the prejudice angle, as historically they have tended towards having far less diverse populations, in terms of religion, culture, and race. As I say, I'm pretty sure they've worked hard to create this impression of social progression, and being on our side of the world a great many people seem to have bought it.
Social conservatives don't like gays on religious grounds, or out of simple stupidity. This is true anywhere else in the West as well. In the US we just have a larger fundamentalist base to overcome.