The musical is not about gay people. The underlying theme in the film, providing dramatic conflict in its plot, is prejudice. The song stands on its own, and its message is clear. The introductory dialog is irrelevant, but I'll make a transcript, just for you. I can't guarantee that it will be exact, because my hearing has never been the best.
The character with the accent: What makes her talk like that? Why do you have this feeling, you and she? I do not believe that it is born in you! I do not believe it!
The singer: It's not born in you. It happens after you're born. . . .
Prejudice based in religion is still prejudice. It isn't due any deference. The people who, because of their religion, have carefully taught their children to feel prejudice toward certain other people don't wish for their teachings to be contradicted by the public schools. At least in the modern western cultures, their religion doesn't give them the authority to dictate what is taught in public schools, any more than a racially prejudiced person can dictate that their child not be taught about tolerance and mutual respect.